Northwest Dragonflier

Seeing Red: Cardinal Meadowhawk

2012-02-20T12:53:00.000-08:00

Most meadowhawks (Sympetrum) are red—at least the males are, and sometimes the females too—but the Cardinal Meadowhawk (S. illotum) is about as red as they get. Mature males are simply vivid. Among the first spring-flying dragonflies in the Pacific Northwest lowlands west of the Cascades, it’s a welcome splash of color after a damp, dreary winter. Look for them at marshes and well-vegetated ponds and lakes of all sizes. Check out this map at OdonataCentral and see if this species has been recorded in your area.

They are also pretty easy to identify between the abdomen lacking any black patterning (which I think amplifies the redness), the red face, the brown thorax with a pair of white spots on the side, and wings with short basal black streaks enveloped in an amber suffusion and bright saffron veins along the leading edge. Females are either brownish or reddish in color, but either way they have the same white spots on the thorax and the short black streaks at the wing bases—a unique character among our meadowhawks.

Female Cardinal Meadowhawk (Sympetrum illotum). Notice the pair of white spots on the thorax and the short black streaks at the wing bases.

In the Pacific Northwest, we have several weeks yet before we can reasonably expect to see Cardinal Meadowhawks (or any adult dragonflies for that matter), but keep an eye out for them on those pleasantly warm, sunny, t-shirt appropriate days in April and early May (earlier further south)—weather permitting, of course!

A Checklist of North American Odonata, 2012

2012-02-17T14:38:00.000-08:00

Click image to open the PDF.

Just a quick message to let you know that the 2012 edition of A Checklist of North American Odonata by Dennis Paulson and Sidney Dunkle is now available. You can find the PDF (just over 1 MB) here at OdonataCentral.org. You can also just click on the image at right to open it.

Originally published by the Slater Museum of Natural History, University of Puget Sound, in 1999, this document isn’t simply a list since it contains a wealth of information on each species recorded from the continental United States and Canada. In each species entry you can find reference information for the original description, the type locality, etymology of the scientific and English names, and a brief description of its range. Similar information is also presented for each genus.

A sample from A Checklist of North American Odonata, 2012 edition.

The introduction has information on the number of species and genera in each family and suborder, the number of newly described species by family and by decade, and on the adoption of standardized English names. At the other end of the document, the extensive annotated bibliography indicates which genera and species were described in each publication, and the appendix wraps it up with a list of synonyms.

If you’re serious (even just mildly serious) about Odonata in North America, this document is a must-have, and since it’s free, you can’t argue about the price!

The Rest of the Story

2012-01-30T17:05:00.000-08:00

A picture is worth a thousand words, as the saying goes, but that doesn’t mean that there aren’t many more words lurking behind the photo which tell a much more interesting story.

What do you see in the photo above? The primary subject is a dragonfly—a female Grappletail (Octogomphus specularis) to be exact, a species of clubtail in the family Gomphidae. What is the slender blue “stick” that this Grappletail is grappling? That is the abdomen of a male Vivid Dancer (Argia vivida)—a damselfly, his head and thorax in the dragonfly’s digestive tract by the time this photo was exposed. Odonate-on-odonate predation is always interesting when you see it, but not so uncommon that it’s ever a surprise—especially in cases like this when the predator is significantly bigger than the prey.

That photo was taken at Gold Lake in the central Oregon Cascades—a special place for a number of reasons. One of them is the large numbers of Grappletails that congregate where the waters flow out of the lake and become Salt Creek. Dozens and dozens of them can be seen sitting all over the place—on boulders, on logs, on the bridge over the creek, on the surrounding vegetation, and on you. I have photos of up to 13 of them perching on a single boulder. It is really odd to see so many individuals of any clubtail (or any dragonfly species, for that matter) together at one place. It’s also a very enjoyable place for photography since there is at least one Grappletail everywhere you look, and they are often very approachable.

Here's a better view of a different female Grappletail (Octogomphus specularis) at Gold Lake.

During a Gold Lake visit in August of 2007, I was trying to photograph a female Grappletail that was sitting on a log, but as I was looking through my camera’s view finder, a blue blur kept buzzing her head and she flew up each time to chase the annoying meddler away. This wasn’t working out for me, so I lowered my camera to see what was going on. The intruder was a damselfly—a male Vivid Dancer (Argia vivida). What was he doing? Well, I couldn’t be positive, but it sure looked to me like the little guy was trying to go into tandem with the relatively gargantuan Grappletail (with the ultimate goal of copulating, presumably). I guess he had a fondness for Amazons.

I know, I know, this seems pretty fantastic, but each time the damsel dropped down, he curved his abdomen forward as though he intended to clasp her behind the head with his abdominal appendages. I can’t imagine what else could have possibly motivated him to do such a thing. The mere notion that a damselfly would even attempt to go into tandem with a dragonfly—one twice his length, really blows my mind. It’s unheard of as far as I know. Assuming that I correctly assessed the dancer’s intentions (I concede that I could be wrong, but I can’t imagine what else was going on), it raises some interesting questions such as, Can a damselfly really know whether a dragonfly is a male or female, and if so, how?


An intact male Vivid Dancer (Argia vivida) wisely copulating with a female of his own size.

It’s funny to think about what it would have looked like if he was successful, if she was receptive, and they actually got tab A into slot B. Take a look at the copulating pair of Vivid Dancers at right, and just try to imagine that the female (the non-blue one) is a dragonfly about twice as long as the male and quite a bit chunkier. Completing that circle would put some serious stresses on the joints!

Naturally, the Grappletail was having none of it! She chased the little dancer away four or five times, returning to her log after each flight. Unfortunately for him, he made one too many attempts. The last time he dropped down, she flew up, chased him, grabbed him in mid-air, and perched in streamside trees to make a meal of the little love-struck damsel. That was when I snapped the photo at top, and that’s the rest of the story.

Mite-y Dragons: Odonata and Water Mites

2012-01-22T18:53:00.000-08:00

If you look at odonates often enough, closely enough, you’re bound to notice some that areaccessorized with tiny orbs—often orangish or reddish in color, clinging tovarious parts of the body like jewelry. But it isn’t “bling” or the latest fadin body art. When I first started catching odonates and looking at themin-hand, I thought they might be eggs which got stuck to the body, but thatisn’t right either. What are these sanguine spheroids, these rusty rondures, theseblushing bulbous globules?

Male Tule Bluet (Enallagma carunculatum) with a string of mites under the abdomen.

These are ectoparasites—meaning that the host–parasite interaction occurs onthe outer surface of the host rather than internally. More specifically, theseare larval water mites or Hydrachnida, which are in the same class ofarthropods as spiders, scorpions, ticks, and their colleagues. Water mitesthat use odonates as hosts are predominantly species of Arrenurusin the family Arrenuridae—of which at least 55 species have been described asectoparasites of Odonata so far.


Top: Male Alkali Bluet (Enallagma clausum) with a couple of mites tucked under the thorax between the middle and hind legs. Do you see them? Bottom: Male Pacific Forktail (Ischnura cervula) with a single mite on his "shoulder" above the base of the middle leg.

Water mites that are attached to an adult odonate actually initiatedtheir relationship underwater during the odonate’s nymph stage. Thefree-swimming larval mites find final instar odonate nymphs and cling to them,but they are not parasitic at this point—they just try to find a place on thebody where they can hang on and avoid being knocked off when the nymph groomsitself (under the wing pads, for example). It would be interesting to know howthe mites determine which odonates are nearing emergence and which are not.When the odonate emergesfrom the water to become an adult, the mites crawl from the exuvia (the shednymphal skin) onto the just emerged adult (which is probably still goingthrough the process of expanding its abdomen and wings), and attaches somewhereon the body while the exoskeleton is still soft and easy to pierce. The mites most often attach to the ventral areas of the thorax or abdomen. Rarely you see them higher on a dorsal surface or on the head, and they sometimes even attach to the major wing veins although I’ve never seen this myself. Apparently attachment site preference varies by mite species.

Finding a meal isn’t the only objective for the mites. They want to traveltoo. The technical term for this is phoresy—the use of one animal byanother for transportation. Lots of mites are phoretic, at least during some stage of their life cycle, and they use avariety of arthropods and other animals for transport. Why do mites want to travel? There are anumber of potential benefits of dispersal among which are finding food (orhosts), finding habitat, expanding the species’ range, and increasing geneticvariation by reproducing with individuals from other populations.

Male Eight-spotted Skimmer (Libellula forensis) with a number of mites on the thorax and one on his head below the eye.

Eventually the odonate host returns to wetland to reproduce (this may be theplace where it emerged or it may be someplace else). When this occurs, theirhydrachnid passengers—fully engorged and significantly bigger than when theyfirst found their host, have their opportunity to unplug and take a triplegainer into the water where they can continue their life cycle. So theparasitic use of adult odonates by water mites is temporary.

Although odonates carrying water mites typically appear to be healthy andenergetic, studies indicate that their longevity, flying endurance, and reproductive success canbe negatively impacted by the stowaways. This seems to be especially true whenlots of mites cluster together and cause significant damage to the cuticle ofthe exoskeleton, perhaps leading to desiccation. I assume that clusters of mitesat particular locations on the odonate body—until they drop off anyway—can also interfere withreproduction by impeding copulation or by blocking sperm transference to themale’s secondary genitalia. It seems that just a few mites attached to unobtrusive areas ofthe body have negligible impact, and it’s more of a commensal relationship inthat case.

Left: Female Lyre-tipped Spreadwing (Lestes unguiculatus) with several mites on the thorax and another about halfway down the abdomen. Right: Male Spotted Spreadwing (L. congener) with a cluster of mites near the tip of the abdomen and another single about halfway up. I can't see how the male can transfer sperm to his secondary genitalia with all those mites there.

It’s interesting to consider which odonates are frequent water mite hostsand which are not. Water mites occur primarily in non-flowing (lentic) orslow-flowing waters, so naturally, odonates which prefer those habitats are good candidates. In general damselflies (Zygoptera) seem to hostwater mites more often than dragonflies (Anisoptera); however certaindragonflies in the skimmer family (Libellulidae) are parasitized regularly andthese include the pondhawks (Erythemis), whitefaces (Leucorrhinia),king skimmers (Libellula), and meadowhawks (Sympetrum). On theother hand, some other groups of dragonflies—for example darners (Aeshnidae),occur in lentic habitats too, but they rarely host water mites. Are the mitesdiscriminating or are these dragonflies somehow mite-resistant? I don’t know.Maybe the nymphs of these dragonflies are more skilled at evicting stowawaysbefore emergence.

Left: Male Striped Meadowhawk (Sympetrum pallipes) with a number of mites on the thorax. Right: Female Band-winged Meadowhawk (S. semicinctum) very heavily infested with mites. This is one of the worst cases that I've ever seen and it can't be good for the host.

So keep an eye out for odonates carrying these little hitchhikers and thinkabout how far they may have traveled and how far they still have to go beforethey dive into a pond. At least they get a meal with their flight which is morethan I can say for my flying experience lately!

Further Reading

Some of the information I present here was gleaned from Philip Corbet’smonumental Dragonflies: Behavior and Ecology of Odonata published in1999. I recommend that you start here if you’d like to read more about thistopic (or pretty much anything having to do with odonates). Every time I crack open this tome I learn something new.

I also found an online PDF of a 2006 paper by Andrzej Zawal on the use of odonates by Arrenurus larvae at a lake in Poland, and this indicates that odonate nymphs are sometimes parasitized by mites too. You can find that PDF here. Perhaps some species of mites are parasitic on odonate nymphs and others are strictly phoretic until the odonate emerges.

Protoneura: Sparks in the Dark

2012-01-15T16:28:00.000-08:00

Considering that it’s January and that I can’t reasonably expect to see an adult odonate for a couple of months in the damp, chilly Pacific Northwest, I thought I’d take you back to Ecuador to profile one my my favorite genera of damselflies.

The Protoneura (21 known species) are small, but relatively long, skinny damselflies in the family Protoneuridae—the “threadtails” as they are known commonly. This is a mostly tropical family found circumequatorially, but three species make it as far north as southern Texas. Male Protoneura are often brightly colored, at least on the thorax, but they also stick to shady areas along forested streams where they can be difficult to spot. It’s not unusual to notice a bit of bright color suspended over a small stream, then realize that it’s part of a Protoneura hovering motionlessly.

Below are the four species of Protoneura that I have photographed in Ecuador. Two of them (scintilla and woytkowskii) were in the Amazonian lowlands and the other two (macintyrei and amatoria) were in the Pacific lowlands.

Male Protoneura scintilla in Sucumbíos Province, Ecuador. A rather dark species overall except for the orange "flames" on the thorax.

Male Protoneura woytkowskii in Sucumbíos Province, Ecuador. A lot more orange color on this one extending onto the tops of the eyes and the legs, as well as a bit near the tip of the abdomen. The hovering Protoneura at the top of this post is also this species.

Male Protoneura macintyrei in Los Ríos Province, Ecuador. Similar to woytkowskii above, but note the difference in thorax pattern and eye color.

And now my favorite...

Male Protoneura amatoria in Manabí Province, Ecuador. The vivid red color on these is spectacular and surprisingly difficult to spot in deep shade.

Pair of Protoneura amatoria ovipositing in tandem. Protoneura typically oviposit on floating vegetation and debris, the female bending her abdomen so much that it is wedged up between her wings and nearly comes into contact with her thorax; the male usually assumes an erect "sentinel" position, often flapping his wings to maintain support. This pair was ovipositing on a loose piece of wood and the flapping male propelled their little "boat" across this small stream-side pool, although I assume that was unintentional.

The Spotted Spreadwing (Lestes congener): A Quick Look

2011-11-19T10:03:00.001-08:00

A reader recently requested that I write a post on the spreadwings (Lestes) in the region—something I had been thinking about for a while, but I haven’t been able to sit down at the blog machine much lately. So for now, I’ll just present a few words and images of one of the more common Northwest Lestes, and the one which is most expected during the tail end of the season in this region (and I think over much of its range, which is a significant portion of the United States and southern Canada).

Male Spotted Spreadwing, Lestes congener
(close-ups of the photo at top): the head and
thorax above, the end of the abdomen below.

The Spotted Spreadwing (Lestes congener) is fairly distinctive among the Northwest species: its thorax is mostly slaty gray over the dorsal areas with minimal, if any, metallic colored reflections, and largely lacking obvious pruinescence; the pale antehumeral (“shoulder”) stripe is very thin and light brown in color—never pale blue or greenish-blue; the pale pruinescence at the tip of the abdomen is limited mostly to the last two segments—S9 and S10, with just a thin, partial coating dorsally on S8.

There is often times a very thin pale median stripe on the thorax too, but not always. There are one or two dark elongated spots—what this species is named for, low on each side of the thorax, and often visible from a lateral view (see the female below). Other species, at least sometimes, have these too, so don’t assume you’re looking at this species if you see spots.

If you can see them, the males’ paraprocts (lower abdominal appendages) are short—about half the length of the longer curved cerci (upper abdominal appendages). The Archilestes (California and Great Spreadwings) have short paraprocts too, but they are noticeably bigger species with unique thoracic patterns. Our other Lestes, however, all have longer paraprocts. As always, I encourage in-hand examination if you want to make sure.

Female Spotted Spreadwings are very similar to males in overall pattern and coloration, but have little pruinescence, especially on the abdomen. Their eyes are always brown unlike the females of our other species which are sometimes, at least, blue (the females of some species are polychromatic with either blue or brown eyes at maturity). The ovipositor is relatively short, but this can be difficult to judge without experience or comparison to other species. Some other species have short ovipositors too.

Female Spotted Spreadwing, Lestes congener.

The species most similar to Spotted Spreadwing in this region is the Black Spreadwing (Lestes stultus—possibly a subspecies of Emerald Spreadwing, L. dryas, but currently considered a valid species), although it is largely restricted to lower elevation and foothill areas of Northern California and southwest Oregon. It also has an earlier flight season (with some overlap).

The Black Spreadwing has a more robust build—females especially, and quite often has more obvious colored metallic green, purple, or bronze reflections on the thorax (sometimes abdomen too). The males’ paraprocts are longer with angled tips that are vaguely foot-shaped; the female’s ovipositor is a bit longer and more hefty.

Another difference is that male Black Spreadwings often, but not always, have more extensive pruinescence at the end of the abdomen, extending more noticeably onto S8. I’ve also noticed a little difference in the shape of the pale antehumeral (“shoulder”) stripe—at least on males: on Spotted it tends to be a little constricted before a more bulbous tip at the posterior end; on Black it is more evenly tapered. This is a subtle difference and subject to variation (like all characteristics). Again, I encourage in-hand examination of the structural differences if you want to be certain.

So look for the late-flying Spotted Spreadwing if you still have some decent weather in your area—I’m thinking the warmer parts of Northern California at this date. I don’t expect to see anything in my neck of the woods until next spring, but it will be much longer until the Spotted Spreadwings are out again!

Another late visit to Ice House Lake

2011-11-10T18:25:00.001-08:00

Facing a forecast of 60°F and sunny skies on a day off from work, I couldn’t pass up the chance to get out to one of my favorite spots in the region and see what was still flying. I went out to Ice House Lake which is just off the Columbia River in Skamania County, Washington. I wrote about a previous visit here in Recent Outings on the Lower Columbia.

Many of the species I saw on that previous trip were still flying today, but in smaller numbers in some cases (as would be expected on this late date). The dominant species today where California Spreadwing (Archilestes californica) and Autumn Meadowhawk (Sympetrum vicinum; the ovipositing pair above), both still going strong. There were also a few Saffron-winged Meadowhawks (S. costiferum), several darners—the two I saw well were Shadow Darners (Aeshna umbrosa), and a few Tule Bluets (Enallagma carunculatum). Below are a few photos from today...

California Spreadwings (Archilestes californica): two males sharing a perch on the left; a female on the right.

Male Autumn Meadowhawk (Sympetrum vicinum) on the left; male Saffron-winged Meadowhawk (S. costiferum) on the right.

Odonate Magnet

I was frequently used as a perch if I stood still in the sun. Mostly it was Autumn Meadowhawks that were trying to sun themselves on me, but a few California Spreadwings landed on me as well. One spreadwing landed on my thumb and just wouldn’t leave, so I took a few close-ups of him.

A male California Spreadwing (Archilestes californica) on my thumb.

A male Autumn Meadowhawk (Sympetrum vicinum) on my leg.

Obelisking

I found one male Tule Bluet (Enallagma carunculatum) which was obelisking, but rather than for keeping cool on a hot day, it was trying to warm up on a cool day. This was the first time that I noticed an odonate obelisking for this purpose. Read more at Obelisking: Sticking it Where the Sun Shines. The pond damselflies don’t obelisk as much as some other groups of odonates, and when they do, they don’t really get the abdomen hoisted up very high. Maybe they don’t have the muscle strength needed to get that long abdomen (relative to the thorax) very far above the horizontal.

A male Tule Bluet (Enallagma carunculatum) obelisking in order to warm up—raising its abdomen up to absorb more solar radiation.

I also photographed an Autumn Meadowhawk (Sympetrum vicinum) perching on the sunny side of a wooden stake. This oriented his body nearly perpendicular to the relatively low sun. In a sense, this was kind of a “lazy obelisk” since he was just hanging on the side of an object; or maybe “smart obelisk” is more appropriate since he was expending far less energy (I presume) than if he was holding his abdomen up in the air. What do you think?

Male Autumn Meadowhawk (Sympetrum vicinum).

Another Aeshna

Lastly, here’s a photo of a Shadow Darner (Aeshna umbrosa) which let me get one shot before it bolted. Can you see all the characters that point to this species? Review Sorting Paddle-tailed and Shadow Darners Out-of-Hand if you’re not sure.

Male Shadow Darner (Aeshna umbrosa).

Halloween Fun

2011-10-31T06:33:00.000-07:00

Greetings from the Umbrosa System in the Aeshna Cluster.
Take me to your Odonatist...

Sorting Paddle-tailed and Shadow Darners Out-of-Hand, Part 2

2011-10-30T12:20:00.000-07:00

This is the continuation of Sorting Paddle-tailed and Shadow Darners Out-of-Hand, Part 1. Read that post first if you haven’t already...

4m. S10 With/Without Pale Dorsal Markings (Males Only)

Left to right: typical male Shadow Darner with black S10
male Paddle-tailed Darner with blue on S10; atypical
male Shadow Darner with blue on S10.

This character is often pretty easy to see and assess on perching individuals: the top of S10 (the posterior-most abdominal segment where the cerci and epiproct are attached) is either all black (Shadow Darner) or clearly has blue spots—often partially fused (Paddle-tailed Darner).

I have some male Shadow Darner specimens with small, very obscure pale areas on S10 which may not even be visible in the field. However, I have photos of one exceptionally colorful (more blue than normal) individual which had obvious pale markings on S10, although they were less well-defined than they are on Paddle-tailed. If it wasn’t for that individual, I might have ranked this character a little bit higher in usefulness. On the other hand I have yet to see the opposite variation (lack of, or very small and obscure spots) on male Paddle-tailed Darners, although it’s not impossible. I suppose the rule of thumb here is that if S10 clearly lacks any pale markings, Shadow Darner is a safe bet; the presence of obvious, sharply-defined pale markings very likely indicates Paddle-tailed, but consider the possibility of odd-ball individuals. Again, I remind you to not rely on any single character if possible.

Female Shadow Darner on left; female
Paddle-tailed on right. S9, S10, and
bases of broken cerci. On both, note
the small pale areas on the posterior
edge of S10 where the cerci attach.

This character actually works pretty well for females too, but because of some complicating factors I decided to make it a “male only” character. First, on female Paddle-tailed those pale S10 spots tend to be smaller and less well-defined compared with males, so a closer look is often required to evaluate them. Another complication is that small areas on the posterior edge of S10 adjacent to the cerci are usually conspicuously pale on females of both species. On Paddle-tailed Darner, these don’t stand out as separate spots from the usual bigger pale spots unless you get a very close look; on Shadow Darner you may see those pale areas on the posterior edge and not realize that they aren’t the spots (see the comparison at right). Those images show a big difference on S9 too (the uppermost segment), but that is quite variable on Shadow Darner.

4f. Shape of Dorsal Abdominal Spots (Females Only)

Female Shadow Darner on left; female
Paddle-tailed on right. Middle abdominal
(part of S3 to S7) segments.

This is one of those tentative characters which appear to be helpful at this time, but that could change with additional observations. There are two things to look at on the middle abdominal segments (primarily S4–S6): the pair of spots at the posterior end of each segment and the smaller, roughly triangular spots just anterior of middle (I’ll refer to them as “middle spots” for brevity).

On female Shadow Darners, the posterior spots are usually narrow bars with a more-or-less flat (can be slightly convex or slightly concave) anterior edge; the middle spots are vary narrow and only slightly triangular with the inner ends just a little wider than the outer. If they are more clearly triangular, the inner side is less than half the the length of the anterior side.

On female Paddle-tailed Darners, the posterior posts are more oval with a clearly rounded anterior edge (there may be small concave “divets” along that edge); the middle spots are more obviously triangular with the inner edge more than half the length of the anterior edge.

5m. Epiproct Color (Males Only)

I started noticing in my photos that the epiproct (the lower abdominal appendage) on male Shadow Darners, when viewed dorsally, is mostly very pale off-white with a black border. The epiproct on most male Paddle-tailed Darners is all dark (medium brown in the middle if you get a close look), however there seems to be some regional variation in this. You can see the differences in images in section 4m above—it’s pretty obvious when you compare the two Shadow Darners (left and right) with the Paddle-tailed (middle). The epiproct is the shorter appendage between the cerci.

This difference appears to hold up pretty well over most of the Northwest, however I have some specimens of Paddle-tailed Darner from the very arid Alvord Basin in southeast Oregon (part of the Great Basin) which have pale epiprocts very similar to Shadow Darners. I’m going to keep an eye on this character, but it seems to be useful in the more humid, cooler parts of the region, at least.

5f. Presence/Absence of Cerci (Females Only—NOT Reliable)


End of abdomen of Shadow Darner on the left; Paddle-tailed on the right.

This is not a reliable identification character, but it’s interesting enough to merit mention. It is not unusual to come across mature female darners that are missing their cerci. Presumably they break off during daily activities like ovipositing, or maybe during copulation. Female Shadow Darners are a little different in that they lose their cerci at such a high rate that it seems to be routine for them. I don’t have a single photo or specimen of a female Shadow Darner with her cerci intact, but I do have many examples of other species in possession of them. I’d say that any obviously mature female Aeshna with intact cerci during the latter end of the season (well after most have emerged) is very likely not a Shadow Darner, but definitely don’t rely on this alone.

I can’t help wondering if female Shadows remove their cerci intentionally as some kind of signal—that they are mature enough to copulate, or that they have already copulated. I don’t know, but I can’t imagine why else they would lose their cerci so much more often than other female darners. A couple of times I caught a female Shadow Darner and, as soon as I pulled her out of the net, the end of her abdomen curled toward the mandibles and “snip, snip”—both cerci fall away. In those cases it was certainly self-inflicted, and the fact that both cerci were bitten off—not just one of them, suggests to me that it wasn’t an “accidental”, random event. We may never know for sure, however.

6m. Shape of Anterior Thoracic Stripes (Males Only)


Left to right: male Shadow Darner with continually widening anterior thoracic stripes; male Paddle-tailed Darner with constricted stripes; male Paddle-tailed Darner with broken stripes.

Most male Shadow Darners have relatively heavy anterior thoracic stripes which continually widen from front to back (wedge-shaped). On most male Paddle-tailed Darners those stripes are usually either constricted or completely broken just before the terminal expansion.

There is some overlap in this character: occasional male Paddle-tailed Darners have anterior thoracic stripes which appear parallel-sided before the terminal expansion, and some male Shadow Darners have a very slight constriction before the terminal expansion. For now it appears that this character is useful if it is either wedge-shaped or obviously constricted (or broken), and anything in-between is not useful. As always, don’t rely on any single character whenever possible.

7m. S2 Mid-Dorsal Stripe (Males Only)

The dorsal surface of S2. Two male Shadow Darners on the left; three Paddle-tailed on the right.

This one certainly needs further assessment, but it appears that the mid-dorsal stripe on male Shadow Darners is typically complete and expands (either at a spot or into a funnel-shaped terminus) anterior of the perpendicular stripes on either side; on male Paddle-tailed Darners the mid-dorsal stripe on S2 is complete or broken and often without any obvious expansion; if it does expand at a spot, the expansion is at the level of the perpendicular lateral stripes.

Something I just noticed while looking at these is that Paddle-tailed Darner has a wide black posterior margin on S2, while Shadow Darner has an extra thin blue line within the black margin. That extra blue line is not always well-defined, but it is present on all of the male Shadow Darners that I have photographed. I also see some differences in the adjacent areas of S3—the extent of blue on the sides and whether they connect across the anterior end of the segment, although that is obviously variable. I’ll look into those some more too.

Conclusion

I’ve always thought of Shadow Darner as darker overall than Paddle-tailed Darner since the lateral thoracic stripes and dorsal abdominal spots average smaller (and maybe the name has a psychological effect too). I have come to realize, however, that Shadow Darner makes up for the limited color in some places with added color in other places—the anterior thoracic stripes and the top of S2 on males, for example. And, of course, they have those ventral pale spots on the abdomen too. You just have to know where to look. Out-of-hand identification really boils down to understanding where Paddle-tailed Darner has more color, and where Shadow Darner has more color.

Over time, I’m sure, some of these characters may prove to be too variable to be very useful, while other potential field marks will come to light. It’s always interesting to see how geographic variation plays a role too—as it appears to do so with male Paddle-tailed Darner epiproct color.

As always, I appreciate feedback, especially if your observations differ from mine.

Sorting Paddle-tailed and Shadow Darners Out-of-Hand, Part 1

2011-10-28T17:40:00.000-07:00

Paddle-tailed Darner (Aeshna palmata) and Shadow Darner (A. umbrosa) are both rather common and widespread—nearly ubiquitous, I’d say—across the Northwest during the latter part of summer and fall. Not only are they superficially quite similar in appearance, but they are also frequently found flying together. Add to this situation the fact that more and more people are relying on photographs and binoculars instead of nets to identify odonates, and it becomes evident that “new” field marks are needed to sort out these bugs. In this post I’ll summarize the various differences between these two species and explain which in particular seem to be the most useful, at least at this time, for “out-of-hand” identification. Some of these have been well-understood for a long time and some have only recently come to light.

The "Classic" Field Marks

When I started identifying odonates in the mid-90s, separating these two species involved the relative thickness of the thoracic stripes, the relative size of the dorsal blue spots on the abdomen, whether or not there were blue spots on the dorsum of S10 (the posterior-most abdominal segment), whether or not there were pale spots on the underside of the abdomen, and whether or not there was a dark face line. The latter three characters work well much of the time, but the others are not only variable, but also quite subjective and difficult to assess without experience and comparative material. You also hear about Shadow Darners frequently having an extension or “flag” at the top of the anterior lateral thoracic stripe. It is more often well-developed on Shadow Darners, but I find it variable enough on both species to be unreliable.

Ruling Out Other Species First

Before you can figure out whether your subject is a Paddle-tailed or Shadow Darner, you have to first know that it is one of those species. These two species (including males and females) have a pair of pale, narrow to moderately wide, relatively straight stripes on the side of the thorax. These are often mostly yellow, but transition to pale blue or greenish-blue at the tops (occasionally more pale blue or greenish-blue overall), and they are pale enough and contrast with the otherwise dark brown thorax enough to be conspicuous from a distance.

Male Paddle-tailed Darner abdominal
appendages, lateral view. You see two
spines because one of those is on the
opposite cercus.

Males have cerci (upper abdominal appendages) which are somewhat flattened, but twisted so they appear relatively wide from the side. Each cercus also has a spine near the tip below the rounded apex which is small, but easily seen through binoculars if you’re close enough, and in good quality photographs (it’s just barely visible in the photo above). I prefer to label this type of Aeshna cercus as “spined”, but you will also see some authors describe it as “wedge” or “paddle” in shape. Males of two other species in this region have similar appendages—Walker’s Darner (Aeshna walkeri) and Lance-tipped Darner (A. constricta), but these are more restricted in range and habitat, and are not frequently encountered in the Northwest. I may discuss those species in a later post.

Females of some other species are very similar to Paddle-tailed Darner and they can be problematic to differentiate. In particular, female Variable Darner (Aeshna interrupta) can be extremely similar when they have relatively bold thoracic stripes. In that case, small structural differences are the only way to confidently identify them and those are difficult to see out-of-hand. Sometimes you just have to accept that not everything is identifiable.

Caveats

I started to go into a long discussion of a couple of issues, then I thought it best to restrict it to some brief statements for this post. 1) Remember variation. Practically every character varies to some degree or another—sometimes a little, sometimes a lot—and the extent of variation of some characters is not yet fully understood. 2) Because of variation, don’t rely on any single field mark whenever possible. These issues really deserve a much more thorough discussion, but let’s keep it there for now and move on...

What to Look For

Differentiating Paddle-tailed and Shadow Darners depends, in part, on whether your subject is a male or female, although some characters work for both. Below is a simple table to guide you. The characteristics are roughly in order of usefulness as far as I have determined, with the most useful at the top. The first three work for both males and females. This ranking is pretty subjective, and is subject to change if better information comes along. In other words, I could easily change mind mind if additional observations warrant it. Some of these criteria I consider tentative and particularly in need of further assessment (indicated with *), but at this point they appear to be helpful (remember the caveats about variation and relying on a single character).

	Males	Females
1	presence/absence of ventral abdominal spots
2	lateral pale mark on S1
3	face line (if either bold and black, or absent—not if thin)
4	S10 with/without dorsal pale markings	shape of dorsal abdominal spots*
5	epiproct color* (regional?)	presence/absence of cerci—not reliable, but worth noting
6	shape of anterior thoracic stripes*
7	shape of pale markings on dorsum of S2*

1. Presence/Absence of Ventral Abdominal Spots (Males and Females)

Male Shadow Darner abdomen, middle segments, ventral surface.

Abdomen of female Shadow Darner on
left; Paddle-tailed on right. Ventro-lateral
view. Red arrows point to the pale spots.

Shadow Darner has paired pale spots on the underside of the abdomen, most prominently on S4–S6 (blue on males—as in image above, blue or tan on females) and Paddle-tailed lacks them being more-or-less uniform in tone/color. Those spots are not so obvious on some female Shadow Darners, but you should see them with a pretty good view. The image at right includes a ventro-lateral view of the abdomen of a pretty dull female Shadow Darner on the left and a female Paddle-tailed on the right. The pale spots don’t stand out so well on this female Shadow Darner and require a close look.

This is by far the best field mark when you can see it—the trouble is that it is often hard to see in the field. Look back at my post Fun With Darners! which has photos of three perched darners. All of the darners I saw that day were perching with their bellies toward the vegetation and it was tricky, at best, to get a view of the underside of the abdomen without scaring them off. If you can get a side view of your subject you may just be able to see the spots if they are there.

Note that a few other Northwest species also have pale ventral abdominal spots, but they are not otherwise especially similar to Shadow Darner and they are more restricted in range and habitat preference.

2. Lateral S1 Pale Mark (Males and Females)

Left to right: the thorax and first two abdominal segments of a male Shadow Darner—the first abdominal segment (S1) is spot-lighted; Shadow Darner S1, lateral view; Paddle-tailed Darner S1, lateral view.

Female Paddle-tailed Darner. The white
arrow identifies the S1 lateral pale mark
adjacent to the black posterior margin.

Paddle-tailed Darners have a vertical, irregularly-shaped (usually thicker toward the bottom) pale mark on the side of S1, adjacent to the posterior black border; on Shadow Darner there is no pale mark adjacent to the black border, but there is an extremely thin pale streak within the black border (sometimes there are only minute traces of that pale streak, and I assume it can be totally lacking on some individuals). In each species I see virtually no variation of this character that approaches the appearance of the other species, and it works for both males and females.

You don’t even need a perfectly lateral view to see that pale S1 mark on Paddle-tailed Darners; even with an oblique view—with the wings obscuring the base of the abdomen, that mark is often visible like in the photo at right. Incidentally, of all of the “spined” darners that occur in the Northwest, the Paddle-tailed is unique in having that irregular pale mark adjacent to the black border. On the other hand, other species which have females that are similar to Paddle-tailed Darner—especially Variable Darner, have that mark too, so just be aware.

3. Face Line—If Either Bold and Black, or Absent (Males and Females)

Left to right: male Paddle-tailed Darner with a bold black face line; female Shadow Darner lacking a black face line; male Shadow Darner with a very thin (not useful) face line.

This character is variable on both species, but it’s a good field mark if that line is rather bold (indicating Paddle-tailed Darner) or if it is absent (indicating Shadow Darner; obviously it takes a pretty good look to see that it is absent). If it is there but very thin it isn’t of any help. I find that male Shadow Darners frequently have a thin dark face line—more so than females. It is important to realize that there is a suture across the face where that line is (when present) and because of the angle of lighting, it can appear dark even when there is no dark pigment. Even in that case it typically appears rather thin and usually brown/gray rather than black, and falls in the category of “not useful”.

This topic is continued at Sorting Paddle-tailed and Shadow Darners Out-of-Hand, Part 2.

Recent Outings on the Lower Columbia

2011-10-23T14:43:00.000-07:00

I was able to get out on a couple of warm, sunny days this week. I may not have that opportunity again around here for several months, so I enjoyed it while I could! Several species are still relatively abundant at this time of year in this area, while others are definitely winding down. Many summer species are gone for the year, of course.

Last Sunday (16 Oct) I went to Ice House Lake in Skamania County, Washington. It’s right across SR-14 from the bridge that spans the Columbia River to Cascade Locks, Oregon. There are often several anglers around the margin, but on that afternoon I had the place, and the odonates, all to myself. It was fun.

A couple of reasons why this place is special is that it’s one of the few places in Washington where the Pacific Clubtail (Gomphus kurilis) occurs, and it has a population of Chalk-fronted Corporal (Ladona julia) which is unusual for a low elevation site (about 175 feet above sea level) in this region. Neither of these species is flying at this time of year, but there is plenty more to keep me occupied. Below are several shots from Ice House Lake.

Saffron-winged Meadowhawk (Sympetrum costiferum) was one of the common species. Here’s a male:

The aptly named Autumn Meadowhawk (Sympetrum vicinum) was also present in good numbers. Here’s a male followed by a female:

The California Spreadwing (Archilestes californica) was the dominant damselfly. Here’s a female:

Present, but definitely winding down in numbers were Tule Bluets (Enallagma carunculatum). This is a male:

On Tuesday (18 Oct) I visited Trojan Park in Columbia County, Oregon. The ponds here are much larger than the little Ice House Lake, but had a bit less diversity. It’s always interesting to see how different locations differ in species diversity and abundance at the same time of year.

I saw no Saffron-winged Meadowhawks at Trojan Park, but Striped Meadowhawk (Sympetrum pallipes) was abundant (vs. only one or two at Ice House Lake). Autumn Meadowhawk seemed to be similar in abundance at the two locations. Trojan Park also lacked California Spreadwings, with only the little Tule Bluet representing the damselflies.

Here’s another male Autumn Meadowhawk:

A female Striped Meadowhawk:

A very cooperative female Olive Clubtail (Stylurus olivaceus) which wandered over from the Columbia River, no doubt:

Also at both locations were a number of Paddle-tailed and Shadow Darners (Aeshna palmata and umbrosa, respectively). I got a number of shots of both species, but I’ll save those for an upcoming post on differentiating them.

Fun With Darners!

2011-10-15T20:12:00.000-07:00

The sun made an effort to shine this afternoon (with variable success), and temperatures hovered around the very low 60s. I figured I should take the opportunity to get out and see what I could find flying, so I wandered the grounds and trails of the Columbia Springs Environmental Education Center in Vancouver, Washington.

There wasn’t much variety. Other than a single meadowhawk (Sympetrum) that I spooked from a walkway, all I saw were darners (Aeshna). Two species of Aeshna, Paddle-tailed Darner (A. palmata) and Shadow Darner (A. umbrosa), are particularly common and widespread across the Pacific Northwest during the latter part of the season—mostly from around July on; into November if there are lingering warmish, sunny days. These two species are also very similar in appearance, at least superficially, and are often found flying together.

Today I saw a few darners patrolling the wetlands or hawking insects high overhead, but most of the action was at patches of Himalayan blackberry where many darners were perching and soaking up as much solar energy as they could. The best spots were along trail cuts in the blackberries where the darners would perch on the bramble “wall” that was facing the sun.

Perching darners don’t often let you get very close and they very frequently fly off before you even spot them. I tried really hard, moving slowly and stopping periodically to scan the sun-soaked vegetation before continuing. I did spot some perching males and I was able to photograph a few of those before they took off, but many more got away. I don’t know how many times I stopped to look over the vegetation, not see anything, then spook up one or more darners that were right in front of me as I started moving again. The colorful males are hard enough to spot while they’re perching, but the relatively dull females are even more challenging. I was able to photograph one female which reperched shortly after I spooked it.

Once you spot a perched darner, you have to approach very slowly and make no sudden moves. Some individuals are more approachable—maybe because they haven’t warmed up enough, and I was even able to catch one by hand for a few in-hand photos (I didn’t take a net out with me today).

I plan to offer a thorough comparison of these two darners in a future post, so for now I just offer you a few photos from today. I’m going to leave them unidentified for the time being, but both Paddle-tailed and Shadow Darners are represented. See what you can do with them and feel free to comment on what you think each one is.

A male...

Another male...

A female...

A hand-held male...

Just a Photo: A Table for One

2011-10-14T10:58:00.000-07:00

This was along Mill Creek outside of Walla Walla, Washington a couple weeks ago. There were a lot of meadowhawks (Sympetrum) around—mostly Band-winged Meadowhawk (S. semicinctum) and Striped Meadowhawk (S. pallipes), soaking up a little afternoon sun when the clouds parted. We found this good-sized, plump mantid just off the trail with some Band-winged Meadowhawk remains nearby. I have to assume that the mantid caught and devoured the meadowhawk (its head and thorax, anyway, leaving the wings and abdomen as scraps), and perhaps it was waiting to ambush more that landed within reach of its raptorial forelegs.

The mantid isn’t the native Litaneutria minor, which is a small species (no more than about 1.5 inches in length—this one was about 4 inches) and finely patterned with speckles. I presume it is one of the non-natives, but I couldn’t tell you which one. I wonder if it’s a gravid female with that very plump abdomen—or else she is just full of Sympetrum.

The mantid standing up next to that leaft makes it look like she’s at a dinner table waiting for the next course. She also looks like she is going to pick her teeth with that piece of straw in her forelegs. Wait... ...now that I look at it very closely, I can see that it’s actually an insect tarsus—probably from a mantid. I don’t see her right rear leg, so maybe it’s hers? Maybe it came off in the struggle with the meadowhawk or she tangled with another mantid. I don’t know.

Here’s another view, so technically this isn’t just “a” photo...

Postscript

This appears to be a European Mantis, Mantis religiosa. Thanks to those who commented.

Just a Photo: Chaotic Cluster

2011-09-30T08:00:00.000-07:00

This photo offers a contrast to an earlier post, Just A Photo: A Table for Eight Please? I was visiting Twentymile Creek in southeastern Oregon last year and there were loads of these Sooty Dancers (Argia lugens) ovipositing in tandem on floating leaf debris. It appears that each female is inserting eggs into the underside of the leaves by curving the abdomen up. Unlike the more civilized four pairs of Vivid Dancers (A. vivida) in that earlier post, these four couples are all over the place and all over each other. It takes a little effort to figure out which male is in tandem with which female!

Just as in that earlier post, this is a case of contact guarding—each male remains attached to the female while she oviposits in order to prevent other males from copulating with her and removing or displacing his sperm. This ensures that the eggs she is depositing at the moment were fertilized by him.

ID Challenge #3 Answer

2011-09-27T11:29:00.000-07:00

Click image for a larger version.

All you have to work with in ID Challenge #3 is a pair of wings, but they are patterned very distinctively. A scan through any of a number of field guides to North American dragonflies (of continental or regional scope) would narrow down your choices to two, or maybe three species. That’s the easy part. The challenge is figuring out which one of those is the owner of our pair of wings.

So let’s start at the top: is it a dragonfly or a damselfly? The hind wing is noticeably more broad than the fore wing—particularly at the base, so it’s a dragonfly. You also won’t find any damselfly with a wing pattern like that anywhere in North America (or anywhere in the world as far as I’m aware, but I could be wrong about that).

Now let’s figure out the family. In ID Challenge #1 Answer I talked about using the anal loop in the hind wing to figure out that mystery dragonfly’s family. In this case too, it is more-or-less foot shaped with something that you could call a “heel” and something that you could call a “toe” (see the close-up at right). This puts it in the skimmer family—Libellulidae. [...in the limited sense. This is one of those places where you can get caught in the crossfire of dueling authorities—it depends on who you read. According to some, Libellulidae includes the subfamilies Macromiinae, Corduliinae, and Libellulinae, in which case the foot-shaped anal loop would indicate the subfamily Libellulinae; according to others Libellulidae has no subfamilies, with Macromiidae and Corduliidae being families on their own, and this is the taxonomy that I go with until I see something resembling consensus.]

One of the possible contenders that you might have picked out in a North American field guide is the Prince Baskettail (Epitheca princeps) which has a superficially similar wing pattern, although it can be ruled out on the basis of my statement that our subject occurs in the Pacific Northwest. The Prince Baskettail doesn’t occur west of the Rockies, but let’s consider it anyway just to make sure. It’s in the family Corduliidae [or subfamily Corduliinae] and like other members of that family, its anal loop is more club-shaped with an irregular expansion that isn’t clearly foot-shaped. Something else that rules out the Prince Baskettail is the shape of the dark spot at the base of the hind wing: bar-shaped on our subject; distinctly triangular on the baskettail.

That leaves two choices in the skimmer family, Libellulidae [or subfamily Libellulinae], with wings like ours: Twelve-spotted Skimmer (Libellula pulchella) and female Common Whitetail (Plathemis lydia)—the male of the latter species has a very different wing pattern. [Another taxonomic sidenote is that the Whitetails are sometimes placed in the genus Libellula, but these days most authors place them in Plathemis.] These are both widespread species across most of the continental US and southernmost Canada. You can view distribution maps for Libellula pulchella and Plathemis lydia at OdonataCentral.org.

There are some pretty consistent differences between the Twelve-spotted Skimmer and the female Common Whitetail in the shape and extent of the dark spots on the wings, but it’s helpful to know a couple of venational landmarks to see exactly how they differ. Take a look at the wings on the right (here I’m using the wings of the Western Pondhawk, Erythemis collocata, since they are completely clear and all of the veins are visible): the shaded red spaces are the “triangles”, and the blue dots mark a major junction known as the “middle fork” in each wing. Notice how the middle fork is at the inner corner of a roughly triangular space which is highlighted in green. These are venational features that all dragonflies have in both the fore and hind wings and are easily recognizable once you’re familiar with them. The foot-shaped anal loop in the hind wing should stick out like a sore thumb by now, so you know which family contains Erythemis...

So, take another look at our subject. Let’s start with the dark bar at the base of the fore wing—it extends across the base of the fore wing triangle, but not any further, and the bar does not extend into the triangle itself. The basal bar in the hind wing similarly doesn’t extend much past the triangle (which is hidden within the dark bar). Both basal bars have neat, clean edges along their posterior or trailing edges (the side that is “down” on your screen). Next we’ll move on to the middle spot in each wing which have a very jagged inner edge where they extend inward to the middle fork and filling the triangular space which is highlighted in green above. These features point us clearly to the female Common Whitetail, Plathemis lydia.

On a Twelve-spotted Skimmer (Libellula pulchella), the basal bars extend noticeably beyond the triangles and “ooze” toward the trailing edge along a pretty sloppy edge—especially into the fore wing triangle, and the middle spot does not extend inward as far toward the middle fork, leaving much of that adjacent triangular space clear. So, Twelve-spotted Skimmer has more extensive basal bars and more limited middle spots, the opposite of what you see on female Common Whitetails. Another more subtle difference is that Twelve-spotted Skimmer wings are a tiny bit narrower relative to their length, and Common Whitetail wings are a little wider relative to their length which makes them look stockier.

Here are full-width images of a female Twelve-spotted Skimmer followed by our subject again which we now know to be a female Common Whitetail for comparison. Pick out the triangles and middle forks in each example even if they are obscured by dark spots.

Twelve-spotted Skimmer (Libellula pulchella)

Common Whitetail (Plathemis lydia), female

Of course, you have to watch out for variation which can be especially significant when you’re dealing with the extent of pigments. If you search hard enough I’m sure you can find one or two individuals of either species that don’t fit the mold, and that’s why it’s important to use multiple characteristics when identifying similar species. The differences that I discussed above should make for pretty good rules of thumb, however. More than likely you’ll have the rest of the bug to examine anyway, but I thought this would be a fun and interesting exercise.

Most of those who commented on ID Challenge #3 got it right, so congratulations to them! Something like the wings of female Common Whitetail may be something that you “know”, but you may not be exactly sure how you know what you know. Whether you knew what they were or not, I hope that this explanation was helpful. Until next time...

ID Challenge #3

2011-09-22T11:30:00.000-07:00

It’s time once again for an identification challenge! All you have to go on is this pair of wings (fore wing on top; hind wing below), but it is a species which occurs in the Pacific Northwest. Most people should be able to narrow it down to a couple of options pretty easily, but which one is it?

Leave a comment to let me know what you think it is even if you’re not sure. Comment moderation will be turned on until I post the answer, so they will not be visible in the mean time.

Postscript, 27 September 2011

This challenge is now closed. The answer with a complete discussion is here.

Some Non-Odonate Critters

2011-09-19T16:03:00.000-07:00

When you spend a lot of time searching for odonates, you naturally come across lots of other fascinating animals. I thought I’d share some of the more interesting non-odonate critters that I have photographed over the years. So no dragonflies or damselflies this time around, but I hope you enjoy it.

Doros aequalis, a wasp-mimicking syrphid fly in the central Oregon Cascades. According to commenters at BugGuide.net, this species is relatively widespread across northern North America, but is rather infrequently encountered. The photo I submitted to BugGuide in 2009 is still the only one for this species, so it must be pretty scarce!

Another bee-mimicker, but this time a scarab beetle: Lichnanthe rathvoni. One day I was looking for Olive Clubtails (Stylurus olivaceus) on the Columbia River in Vancouver, Washington, and a bunch of these scattered from the upper part of the beach as I made my way through young willows and cottonwoods. I must have found them at their peak that day because I haven't seen them in such numbers since. Got to love those crazy antennae! Thanks to Chris Marshall for identifying these.

Near a hot spring in southern Malheur County, Oregon, I came across a congregation of young Burrowing Owls (Athene cunicularia) at their den. A few more youngsters and their parents were scattered around the vicinity, but these three posed very nicely at the burrow.

During a late night drive to the Alvord Basin in southeast Oregon, I found several of these katydids, Capnobotes occidentalis, which come in green and gray forms. These are both females with their long, sword-like ovipositors. The gray one was apparently trying to oviposit in the asphalt, but I can't imagine that she got very far. Thanks to Ron Lyons for identifying these.

The drive that produced the katydids above also produced a large number of Great Basin Spadefoots (Scaphiopus intermontanus) on the road. Pretty adorable as toads go, I think.

Hmm, I seem to focus on bee/wasp mimics and here's another one: the robber fly Laphria astur. I found this one on a log while hiking to a lake (to see odonates, of course) in the southern Oregon Cascades. Thanks to Rob Cannings for identifying this one.

A Western Rattlesnake (Crotalus viridis) in Oregon's Alvord Basin. I never have the right lens on my camera for photographing these when I find them, but this one turned out pretty well even if the rattle isn't visible. I think the blue tongue is a nice touch.

I have a particular fondness for tiger beetles, and this emerald green Cow Path Tiger Beetle (Cicindela purpurea) was on a different kind of path (walking/biking) at a great odonate spot—Lake of the Woods in the southern Oregon Cascades.

Yeah, definitely a thing for Hymenoptera mimics. Here are two views of a jumping spider (maybe Phidippus apacheanus) which is an apparent velvet ant mimic. The iridescent blue chelicerae are mesmerizing. This was at a hot spring in Oregon's Alvord Basin—my favorite area to look for odonates.

Obelisking: Sticking it Where the Sun Shines

2011-09-15T20:12:00.000-07:00

Odonates are ectothermic creatures which means that their body temperature is, for the most part, not self-regulated, but is instead regulated by their environment. This is commonly known as being “cold-blooded”, which isn’t really accurate—at least not when their environment is warm. When it is cold out, odonates are cold and aren’t doing much of anything; when it is warm (and sunny) they are quite happy; when it is oppressively hot, well, something has to be done about that—even for these sun-loving insects.

One strategy odonates employ to avoid excessive heat is to simply get out of the sun. On extremely hot days, you may find congregations of odonates of multiple species enjoying the shady side of a tree. Typically it has to be really hot for odonates to resort to that behavior, however. In general, odonates (males in particular) don’t want to miss out on reproductive opportunities at their favorite haunts, and time spent avoiding the sun is time spent not reproducing.

Obelisk of Senusret I in
Heliopolis [Public domain],
via Wikimedia Commons

Another strategy to avoid overheating which is more commonly observed among some odonates is obelisking. This means holding their abdomen up toward the sun so that the long axis is parallel to the solar rays. I’m not sure how long this term has been in use for this behavior, but obviously it was reminiscent of Egyptian obelisks to someone. The advantage of this method is that they don’t have to leave their pond or stream to keep their cool.

How does obelisking help odonates prevent overheating? By aiming their abdomen toward the sun, they reduce the amount of body surface area that receives direct sunlight. Consider the obelisk at right. When the sun is directly overhead, the surfaces that are receiving the highest density of sun rays are the facets at the top (a relatively small percentage of the total surface area); the sides are nearly parallel to the sun rays so they are receiving a much lower density of solar energy per unit of surface. When the sun is low in the sky, it is the long, vertical surface (a relatively large percentage of the total surface area) that is nearly perpendicular to the solar rays, and it receives the greatest density of solar energy.

Male White-faced Meadowhawk (Sympetrum obtrusum), Jackson County, Oregon.

Female Band-winged Dragonlet (Erythrodiplax umbrata), Los Ríos Province, Ecuador.

Another way to think about it is in terms of the size of the shadow cast by the obelisk. When the sun is high in the sky, the obelisk’s shadow is pretty small. This means that the obelisk is absorbing a relatively small slice of the solar energy that would otherwise hit the ground if the obelisk wasn’t there. When the sun is low in the sky, the obelisk’s shadow is very long and, at this time, the obelisk is absorbing a larger percentage of the sun’s energy. The more solar energy something absorbs, the more heat that is produced.

So, for a odonate on a hot, sunny day, obelisking is all about making its profile (from the sun’s point of view), and therefore its shadow, as small as it can in order to minimize the amount of solar radiation that is absorbed by its body. This allows them to regulate their temperature without having to abandon the action at their local pond or stream (as long as it isn’t so hot that they have to seek shade instead).

Male Gray Sanddragon (Progomphus borealis), Graham County, Arizona.

Male White-belted Ringtail (Erpetogomphus compositus), Wheeler County, Oregon.

Not all odonates employ this technique for staying cool. Among dragonflies you see it most regularly in the clubtails (Gomphidae) and skimmers (Libellulidae), and within those families particular species are frequent practitioners while others don’t seem to do it at all. The Blue Dasher (Pachydiplax longipennis)—like the one in this blog’s title banner, is one of those frequent practitioners. The tropical Micrathyria also frequently obelisk, and three species are shown here.

Male Spot-tailed Dasher (Micrathyria aequalis), El Oro Province, Ecuador.

Male Micrathyria ocellata, El Oro Province, Ecuador.

Male Micrathyria pseudeximia, Manabí Province, Ecuador.

I’ve read that the impressive Dragonhunter (Hagenius brevistylus)—a huge clubtail of eastern North America, has its own variation which is to point its abdomen down, away from the sun, which has essentially the same effect. This is a big, beefy species and I imagine that it takes a lot of energy to hold that abdomen up for any length of time! Perhaps other odonates which typically perch by “hanging” (with the abdomen down) obelisk in this manner too, but it isn’t nearly as obvious as the sunward style.

Some damselflies obelisk as well, although apparently not as often as some of the dragonflies, at least in my experience. In particular the broad-winged damsels (Calopterygidae) and some other groups like the dancers (Argia) are known to use this method of thermoregulation on occasion.

Female Beaverpond Clubtail (Gomphus borealis), Somerset County, Maine.

Female Paiute Dancer (Argia alberta), Harney County, Oregon.

But wait, there’s more! Something I realized only recently while reading Philip Corbet’s monumental Dragonflies: Behavior and Ecology of Odonata (1999)—it’s really impossible to open up this book and not learn something new—is that obelisking isn’t strictly about keeping cool. When the sun is low and the air temperature is relatively cool, an odonate may obelisk in order to warm up. This time the abdomen is not pointed toward the sun, but is instead held up with the long axis perpendicular to the solar rays in order to maximize its exposure. I’m not certain that I have observed obelisking in this context, but I’ll be watching for it.

Don’t Fear the Dragonfly

2011-08-24T16:46:00.000-07:00

I wrote this post several month ago right after starting this blog, then I decided to let it “marinate”. I wondered if maybe I was making too big a deal out of the topic, so instead I wrote and published Do Dragonflies Bite or Sting? as a more informative piece without the psychoanalysis (something for which I have absolutely no training). Since then I have noticed an interesting trend. That post has received far more views than any other post on my blog, and nearly all readers found it with Internet searches using phrases like, “dragonfly bite”, “dragonfly sting”, “do dragonflies bite”, and “do dragonflies sting”, and many other variations along those lines. In fact, those search phrases are the top four phrases which have brought visitors to my blog. So maybe there are a lot more people being bitten or stung by dragonflies than I realize—something which I have a hard time believing, or there really is a lot of fear of being bitten or stung based only on misconceptions. I suspect it’s the latter in a majority of cases. Read on and let me know what you think.

By Dodd, Mead and Company (New
International Encyclopedia) [Public domain],
via Wikimedia Commons

A segment of the population seems to have a deep-rooted fear of dragonflies beyond the regular everyday aversion to “bugs” common to so many. I sense this fear is not the result of direct experience with dragonflies, and I also suspect many of these people don’t even understand why they feel the way they do. I just read that the phobia of dragonflies is called “dragoferosus”—a little party trivia for you. But I’m not talking about something that rises to the level of a phobia—at least I don’t think I am—it’s more of a subconscious fear.

Maybe it has to do with reputation-tarnishing folklore surrounding dragonflies. Names like “devil’s darning needle”, “horse stinger”, “ear cutter”, and “eye poker”, and the notion that during the night they will sew shut the mouths of lying children, scolding women, and cursing men sure don’t help their cause. European folklore frequently associated dragonflies with the nasty red guy downstairs with horns and cloven hooves which doesn’t make anyone popular. I don’t know—I never heard any of this bad press when I was a kid (the 70s primarily), but then maybe that’s why I never had a fear of dragonflies.

Some people certainly do think, or are afraid that, dragonflies will bite or sting them. A few months ago, soon after I started this blog I posted Do Dragonflies Bite or Sting?, and that is by far my most popular post garnering frequent Internet search hits. The short, quick response to this notion is that it doesn’t happen. A free-flying dragonfly will never bite or sting a person as a defensive measure the way a yellow jacket or honey bee might when agitated. Swat at them all you want and there will be no retaliation. The complete answer is a bit more complicated and I go into that in the above post. In the mean time, just remember the short, quick answer and you’ll be fine. So, it doesn’t seem that biting and stinging contribute in a significant way to this general fear of dragonflies.

By Drury, Dru, 1725-1803.
Westwood, J. O. 1805-1893. [Public domain],
via Wikimedia Commons

Maybe it’s the large size of some dragonflies; maybe it’s their command of the air space with powerful yet agile flight; maybe it’s that, at times, they seem to possess a level of sentience, perception, and understanding unmatched by other insects. I admit that I’m biased, but I just don’t get the sense of a conscious, thinking being when I see a butterfly flutter by. On the other hand, when I see a darner busily hunting or searching out females and it hovers for a moment to make a quick assessment of me, there’s a very real sense that there is conscious thinking going on—something far more than instinctual response to stimuli. I’m not saying that there really is this level of conscious thought going on, but the perception that it is occurring is real enough.

I’m reminded of a line from the movie The Mothman Prophecies (2002): Richard Gere’s character asks an old professor-type why the mysterious mothmen were doing what they were doing, and the response was “You noticed them. And they noticed you noticing.” Maybe when it appears that dragonflies notice you noticing, it naturally imparts a sense that they are thinking about you, and maybe that’s a little bit scary to some people?

Whatever reason people fear dragonflies, I have to think that it is based almost entirely on misinformation, misconception, and, maybe in some cases, nothing at all. Cases of biting and stinging only occur in particular circumstances (such as handling them), and even then only rarely. I have been been nibbled by dragonflies while handling them, but that was my fault, and it was always more startling than painful. I have never been stung during the many years that I’ve been chasing them. The benefits of having dragonflies around (by eating other flying insects) far outweigh any remotely possible painful interaction by multiple orders of magnitude. Any other reason to fear dragonflies simply doesn’t have substance.

Trust me. Don’t fear the dragonfly.

It's Time to Watch for Migrant Meadowhawks

2011-08-17T17:31:00.000-07:00

The Phenomenon

Around August and September there’s an intermittent phenomenon at coastal areas of the Pacific Northwest that involves the directional movement of dragonflies (typically southward) and there’s a lot to learn about what exactly is going on. This has been observed most frequently at southern Washington and northern Oregon coastal areas, with sporadic reports from further south into California. This phenomenon is commonly referred to as a migration, but whether it is truly a directed migration (like in the sense that many birds migrate south each year) or something else is one of those things that isn’t yet clear.

A nearly mature male Variegated Meadowhawk (Sympetrum
corruptum). Note the overall reddish-brown color, the pair of
yellow spots on the lower side of the thorax, and the orange
veins along the leading edge of the wings.

These movements of dragonflies primarily involve the 1.5-inch long Variegated Meadowhawk (Sympetrum corruptum), although a few individuals of other species are sometimes reported flying with them. A possible explanation for these directional movements is that Variegated Meadowhawks from northern areas fly to southern US regions in the fall to lay their eggs; their offspring emerge the following spring, and fly back north to complete the cycle. During the southward movement, there seems to be some correlation between flights at coastal areas and east winds: the east winds may push them toward the coast where they then have to take a left turn to avoid the open ocean—the result is a stream of dragonflies heading down the beach. Northward directional movements have not been reported, but spring weather conditions may not have the same concentrating effect, resulting in a more diffuse, cryptic migration.

Some years there are lots of reports of moving meadowhawks on the beaches, and some years there are hardly any. Last year—2010, was a big year for them. So much so, that people who otherwise give no thought to dragonflies at all took notice of the huge numbers, even using terms like “apocalyptic” and “plague”. The events even made headlines at local news outlets such as the Cannon Beach Gazette in Oregon. You can still see their article here.

I think it’s likely that these coastal concentrations are the result of regional topography: East winds are funneled down the Columbia River to its mouth and lots of meadowhawks go with it; when they reach the ocean they resume their southerly course. There have been some reports of meadowhawks flying onto beaches from the ocean (from the west). This suggests that some of them get blown out to the open Pacific, then have to make it back to land (or else become fish food following exhaustion). Looking at this at the bigger scale, our coastal flights may only be a small observable slice of a much more widespread migration that is otherwise invisible because the meadowhawks are so spread out.

Record Your Observations

Immature female Variegated Meadowhawk (Sympetrum
corruptum). The overall color is more yellow with
more obvious white spots on the abdomen and white
stripes on the thorax.

You can help understand this phenomenon. If you happen to observe a lot of dragonflies flying in the same direction (not in flocks like birds—it’s more like a stream) you can really make a contribution. At a minimum, a few minutes to record your observations and a few minutes to let someone know is all you have to do. If you want to put more into it, like formal counts, all the better.

These movements, when they occur, vary widely from pretty light (a few passing a fixed point per minute) to major (in the hundreds per minute) to exceptional (in the thousands per minute). When you’re observing a directional movement of dragonflies the best way to gauge their numbers is to look across a wide open area (like a beach, or an open dune area, or a parking lot) perpendicular to the direction of flight and count the number of individuals that pass your line of sight over a period of time—say five minutes. Divide the total count by the number of minutes to get the rate. It can be helpful to pick a landmark at the other end of your line of sight—a utility pole, a rock, a car, etc., and imagine a “finish line” between you and the landmark.

Additional information that is helpful include the date, location, the times that the flights start and stop (or at least the beginning and ending times of your observations), the direction of movement (determined with a compass, if possible), and general weather conditions—particularly wind direction. If you conduct formal counts like described above, include the length of your line of sight. Of course the species involved is important and if you are unsure of what you’re looking at, photos and video (even of distant subjects) are often helpful for identification later on. As I said earlier, the Variegated Meadowhawk is the primary species seen in directional movements at coastal Northwest locations and I have some photos of that species here and you can view a lot more at BugGuide.net.

Mature male Variegated Meadowhawks are largely red and brown on the body and the variegated patterning gives them a dusty orange appearance from a distance. Mature females tend to be more brown instead of red. Their wings are clear, but the major veins along the leading edge of each wing are orange which can be noticeable at close range. Immature, or more recently emerged, individuals are overall yellow or yellowish-orange with white spots on the abdomen and white stripes on the thorax—each white stripe on the side of the thorax terminates at a yellow spot. The veins along the leading edges of the wings are yellow instead of orange. As they mature, the white stripes and spots darken, but that pair of yellow spots on the side of the thorax persist.

A fully mature male Variegated Meadowhawk (Sympetrum corruptum) without any white spots or stripes.

This male Variegated Meadowhawk (Sympetrum corruptum) is intermediate in maturity still with white spots and stripes, but those are fading.

If you see a lot of Variegated Meadowhawks not flying, but just hanging around open coastal areas away from fresh water like parking lots, parks, and beach areas with drift wood, that’s worth noting too. It may be that a flight just ended and they are taking a break to rest and feed. Maybe the conditions that were good for a flight ended and they are waiting for the right time to start again. Again, recording the weather conditions during your observation may be very helpful.

Report Your Observations

So now that you have some information to share, what do you do with it? At the very least, report your information to an appropriate listserve so that it’s there for others to glean and perhaps combine with other reports. This also alerts readers when a flight may be going on in their area so they can make their own observations. For the northwestern US and western Canada report to the NW_Odonata Yahoo Group; in California it’s the CalOdes Yahoo Group. If you’re not a member of any of these listserves, find someone who is and have them post your information. You can let me know and I’ll make sure that your information ends up in the right place.

Some people collect observations in their local areas such as Mike Patterson (North Coast Diaries) in the Columbia estuary area of Oregon and Washington, and Range Bayer and Terry Morse in Lincoln County, Oregon. At the continental scale, Chris at The Dragonfly Woman is collecting reports of dragonfly swarms (both migratory and feeding swarms) from throughout North America. She has a handy web form where you can report your observations and help out with her research.

Research is also going on at the molecular level to figure out from which latitude, roughly, migrating Variegated Meadowhawks originate. There is a known correlation between the abundance of deuterium (a hydrogen isotope) in the tissues of dragonflies and the latitude where they lived as a nymph and emerged. This analysis, which uses one wing from each specimen, will give us some indication of how far these meadowhawks had traveled at the time they were collected. Dennis Paulson is accepting specimens of Variegated Meadowhawk for this research and he is interested in both recently emerged individuals from local populations and individuals which were part of a directional movement. Either dried or acetoned specimens can be used. He follows the listserves mentioned above so you can contact him that way, or just let me know and I’ll put you in touch.

So get out there and look for migrating meadowhawks. Anyone can make a contribution!

Postscript, 18 August 2011

Dennis Paulson reminded me that major Variegated Meadowhawk flights were also observed at San Juan Island, Washington and in the mountains of western Montana during 2010, so this phenomenon is not restricted to the outer coast. Naturally we’d like to hear about these flights wherever they are observed.

Dennis also elaborated on a Migratory Dragonfly Partnership, including representatives from Canada, the US, and Mexico that will be putting together materials and protocols to involve the public in recording and monitoring dragonfly migration across the continent. The deuterium analysis that I mentioned above is part of this project which is funded by the US Forest Service, through The Xerces Society for Invertebrate Conservation (based in Portland, Oregon). I’m sure we’ll be hearing more about that over the next year.

Now THIS is Recycling: Jumping Spiders Using Dragonfly Exuviae

2011-08-11T13:10:00.000-07:00

When dragonflies emerge and become adults they not only abandon their submerged lifestyle, but they leave behind a natural, albeit temporary, cavity clinging to some above-water surface like a plant, a log, a rock, or even just on the ground. This is their final exuvia—their ultimate nymphal (or larval, if you prefer) exoskeleton within which metamorphosis took place before emergence. These “skin suits” are, of course, biodegradable, but as long as the weather stays dry and it isn’t dislodged by wind, the exuvia can stay intact and in place for some time—possibly for weeks. Why let this little shelter go to waste?

A few years ago Tim Manolis discovered in California that the jumping spider Sassacus vitis uses these translucent cavities as roosting sites and nurseries. The ultimate in green housing! He has since found two other species using dragonfly exuviae: Sitticus palustris and the ant-mimicking Peckhamia (near americana), although the latter may not be a regular user. It turns out that this behavior was known in Europe although it doesn’t appear that it has been investigated very thoroughly. Tim seems to be the only person in North America that is really looking into this and he would love to be informed if you find exuviae being used by jumping spiders (you can contact me and I’ll relay your information to him).

How can you tell when a dragonfly exuvia is being used by a jumping spider? The two that I have found so far I discovered by accident: I collected exuviae and then later found little jumping spiders wandering around the interior of the vials. A closer look at the exuviae revealed silk “tunnels” descending into the abdomen from the opening on the thorax.

Silk threads on the outside of the exuvia may be a clue, but I imagine some silk may be left by non-occupants just passing through too. You may be able to peer into the exuvia through the thoracic opening and see the silk-lined interior and a big pair of jumping spider eyes peering back (or at least glimpse some other body part). If you can’t see into the interior of the exuvia, try looking at it with a light source (the sun or a flashlight) shining from the other side like in the photo below. The dark blob in the abdomen is a jumping spider.

The photographed exuvia below—a Spiny Baskettail (Epitheca spinigera) at Lake of the Woods, was the second one that I’ve found with a jumping spider in residence. Like I said above, I only realized it after I noticed the spider wandering around in the vial that was holding the exuvia. After a short stroll it crawled back inside and that’s when I took the photo.

The first time I found a spider-occupied exuvia, it was that of a Four-spotted Skimmer (Libellula quadrimaculata) at Camas Prairie in the northern Oregon Cascades earlier this summer. I sent that occupant to Tim Manolis and he determined it to be Sitticus palustris. I’m hanging on to my latest find to see if tiny spiderlings emerge—it takes about three weeks for eggs to hatch according to Tim, and this spider seems to be spending a great deal of time in the exuvia as though it was guarding a clutch. Once I see whether “jumplets” are produced or not, I’ll send the adult to Tim so he can determine the species.

So, if you happen to come across dragonfly exuviae, see if you can find spiders within. Tim Manolis wants to know about them—especially from areas outside of Oregon and California since he currently only knows about spider-occupied exuviae from those two states. Information he is interested in includes the dragonfly species that left the exuvia behind and whether any spider eggs are inside (i.e. was the exuvia used for roosting or for nesting). If you can ship the adult spider to him he’ll be doubly appreciative and include the exuvia if you don’t know which species it is. If you don’t know how to reach Tim, contact me and I’ll put you in touch.

Thanks to Tim Manolis for providing lots of helpful information used in this post, and to the fine folks at BugGuide.net for their web site.

Postscript

The spider eventually exited the exuvia and constructed a silk “hammock” in the vial. It turns out that it was a male using the the exuvia while molting. I sent the spider to Tim Manolis and it appears to be Sitticus palustris.

Lake of the Woods, Oregon

2011-08-08T21:38:00.000-07:00

Lake of the Woods is a large natural lake nestled in the southern Oregon Cascades within sight of the sleeping Mount McLaughlin. With easy access right off Hwy 140 and at almost 5000 feet elevation, it’s a popular summer retreat for hordes of campers, boaters, hikers, and day users of all sorts—a recipe which usually keeps me away, but there is a gem of a spot in the middle of it all which is great for odonates.

View Lake of the Woods in a larger map. The rectangle identifies Rainbow Bay.

The gem of a spot is at the easternmost shore of the bay on the eastern side of the lake. That’s Rainbow Bay, and there’s a sedge meadow there which is largely inundated when the lake is at its highest levels during spring and early summer, but becomes mostly dry by late summer and fall. A band of tules hugs the edge of the meadow in deeper water.

View Rainbow Bay in a larger map. The pin identifies the meadow.

This area is easiest to access from dirt pullouts on the side of Dead Indian Road where it passes at its closest. There is also a well-maintained trail that passes through here between the road and the meadow, and connects the Rainbow Bay day use area (to the north) with Sunset Campground (to the south).

This location is well known among Oregon odonatists as the only place in the state where Lance-tipped Darner (Aeshna constricta) can be found somewhat reliably, and I visited on 5 August 2011 in an effort to find nymphs and/or exuviae of that species. I was not successful, but there were plenty of other odonates around to keep me busy.

Things were definitely late up here, as they are all over the Northwest this year. That was most evident in the large number of Spiny Baskettails (Epitheca spinigera) still flying through the open forest around the meadow, and I even found one exuvia of that species still clinging to some vegetation. Normally that species is quite scarce up here by now. Lots of darners were feeding in a loose swarm over the area—three species were represented among the relatively few that I could catch, but the Lance-tipped was not one of them. Clouds of just emerged meadowhawks drifted up from the sedges as I wandered through them.

I haven’t tallied up the complete list of species found at the Rainbow Bay meadow, but below is what I recorded during a few hours on that recent visit. Following that are photos of several of those species taken that day.

Damselflies (Zygoptera)

Spreadwings (Lestidae)

Northern Spreadwing (Lestes disjunctus)
Emerald Spreadwing (Lestes dryas)

Pond Damsels (Coenagrionidae)

Boreal Bluet (Enallagma boreale)
Tule Bluet (Enallagma carunculatum)
Pacific Forktail (Ischnura cervula)
Western Forktail (Ischnura perparva)

Dragonflies (Anisoptera)

Darners (Aeshnidae)

Variable Darner (Aeshna interrupta)
Paddle-tailed Darner (Aeshna palmata)
Blue-eyed Darner (Rhionaeschna multicolor)

Emeralds (Corduliidae)

American Emerald (Cordulia shurtleffii)
Spiny Baskettail (Epitheca spinigera)

Skimmers (Libellulidae)

Chalk-fronted Corporal (Ladona julia)
Hudsonian Whiteface (Leucorrhinia hudsonica)
Eight-spotted Skimmer (Libellula forensis)
Twelve-spotted Skimmer (Libellula pulchella)
Four-spotted Skimmer (Libellula quadrimaculata)
White-faced Meadowhawk (Sympetrum obtrusum)
Striped Meadowhawk (Sympetrum pallipes)
Band-winged Meadowhawk (Sympetrum semicinctum)

Male Boreal Bluet (Enallagma boreale).

Male Emerald Spreadwing (Lestes dryas).

Male Spiny Baskettail (Epitheca spinigera).

Male Chalk-fronted Corporal (Ladona julia).

Male Hudsonian Whiteface (Leucorrhinia hudsonica). This one has atypically small red spots on the abdomen.

Female Twelve-spotted Skimmer (Libellula pulchella). Scarce in forested mountain areas.

Female Four-spotted Skimmer (Libellula quadrimaculata).

Male White-faced Meadowhawk (Sympetrum obtrusum).

Female Band-winged Meadowhawk (Sympetrum semicinctum) with quite a heavy load of parasitic water mites.

Snaketail Emergence Sequence

2011-08-02T15:23:00.000-07:00

A while back I posted a sequence of shots of an emerging American Emerald (Cordulia shurtleffii) which was quite popular. You can see that post here. I love emergence sequences, so here’s another one—this time a female Pale Snaketail (Ophiogomphus severus) in the family Gomphidae, or the clubtails. This was on the Burnt River in eastern Oregon a few weeks ago. Just like last time, I included the time stamp in the upper right corner (hh:mm:ss), so you can see how much time elapsed between each shot.

As usual, emergence was already well underway by the time I could take my first shot in the sequence. Unlike many other dragonflies, clubtails are able to emerge on a horizontal surface and they look kind of odd with only the abdomen still in the exuvia. In this position, I find it suggestive of a cobra rearing up and spreading its hood which seems rather appropriate for something called a snaketail. The white thread is a tracheal lining which stays attached to the exuvia so that it is pulled out of a spiracle (an opening to the tracheal network) during emergence. This allows her to get oxygen from the air now that she is out of the water.

While my attention was elsewhere for a couple of minutes, the abdomen was pulled entirely from the exuvia and she is supporting herself entirely on her legs now. Wing expansion is progressing rapidly.

The wings are pretty much at their full length now, but the abdomen still has some stretching to do.

Now the wings and abdomen are at full, or nearly full length, and the wings are almost totally clear.

My attention was elsewhere again for a few minutes and all that's left is the exuvia which I collected for the record.

Just a Photo: Spiketail Nymph

2011-07-18T15:00:00.000-07:00

I found this bad boy (bad girl, in fact) in a little stream in Oregon’s Blue Mountains a few weeks ago. It’s a full-grown nymph of the Pacific Spiketail (Cordulegaster dorsalis), the only Northwest representative of the family Cordulegastridae. You can’t tell from the photo, of course, but it’s over an inch long. She’s a chunk too—a little lotic tank. Nymphs of this species take five years to get to this size. If it looks dirty, it is—these guys are pretty hairy and all kinds of debris cling to them. These hunters live buried in fine silt and mud with only their eyes protruding so they can watch for prey. You can see what the adult Pacific Spiketail looks like here.

ID Challenge #2 Answer

2011-07-15T15:32:00.000-07:00

I intended to post an answer to ID Challenge #2 much earlier than this, but it just didn’t work out. I’ve been on a road trip to/from Fort Collins, Colorado (for the Dragonfly Society of the Americas annual meeting) and I didn’t have as much down time as I thought I would. During the down time I did have, I was, well… …down. Anyway, better late than never.

Click image for a larger version.

What we have is a rather plain-looking odonate with not a lot of obvious patterning. Let’s work this from the top down. Is it a dragonfly or a damselfly? We can’t tell how big this thing is, but it has a relatively long, slender build, the wings are slender and petiolate (narrowed at the base), and the wings are more-or-less parallel to the abdomen while in the closed position. This all indicates that we are looking at a damselfly. Even during those few times when dragonflies close their wings while perched (like during or right after emergence) the angle of their “hinges” puts the wings almost perpendicular to the abdomen, not parallel to it.

We can also see that this is a female since there is a curved ovipositor underneath the abdomen near the tip. All female damselflies have this sort of ovipositor (used to insert eggs into plant or other material), but only certain families of dragonflies have this kind of equipment.

We can narrow down the choices further if we take a close look at some of the little bits. There is a well-developed vulvar spine just in front of the ovipositor (“S” in the close-up at right). In the Pacific Northwest this eliminates genera like Argia (dancers) and Coeanagrion (Eurasian bluets). This is variable among the Ischnura (forktails)—even within some species.

Now let’s look at the legs. The spines on the tibiae (“T” in the close-up at right) are relatively short. Some genera like Argia (dancers) and Nehalennia (sprites) as well as species in Lestidae (spreadwings) have longer tibial spines—about twice as long as the spaces between the spines, so this feature eliminates those.

What’s left? Well, there are the Enallagma (American bluets), of which several species occur in the Northwest. Females of these species are more boldly patterned with black on the abdomen and thorax and they also tend to have conspicuously pale postocular spots on top of the head. But what if it’s an immature that isn’t displaying typical mature color/patterning? I always like to use structural differences whenever possible to be certain. We also haven’t eliminated the Ischnura (forktails) completely.

Look at that last image again, at the underside of the thorax. There’s an obvious bump there with coarse hairs on it. This points us directly to one genus that we haven’t even mentioned yet: Amphiagrion (red damsels). The vulvar spine and short tibial spines are consistent with this genus too. Amphiagrion is what we have.

The Pacific Northwest species is A. abbreviatum (Western Red Damsel), and females are quite variable both in color and patterning. Some are very dull like this individual, some are more brown or orangish, and some are male-like with a bright red abdomen and a mostly black thorax; some have less black patterning on the thorax, but more obvious black spotting on the abdomen. Whatever their color and patterning, all have that bump on the underside of the thorax which is very helpful.

Several commenters got this one right and I’m sure they spotted that bump. I think it’s important to know the little structural details which are far less variable than coloration and can help you identify confusing individuals like this.