The “anal pyramid” is a more-or-less triangularly-shaped group of five appendages on the posterior end of dragonfly larvae (nymphs) and exuviae, including one epiproct, two cerci (sing. cercus), and two paraprocts.
The author suggests either “posterior pyramid” or “posterior triangle” as a less offensive sounding collective name for these anatomical parts. The author is just saying.
Although the anal pyramid isn’t always shaped like a perfect equilateral triangle, as shown above (in white), it always features the same five component body parts. These parts are often critical for identifying odonate larvae (nymphs) and exuviae.
Nymphs (larvae) in Family Gomphidae (Clubtails) are burrowers that have an anatomy adapted for burrowing into sandy substrates quickly, including a torpedo-shaped body and thick legs with burrowing hooks.
The following videos from the Dragonfly Society of the Americas show two species of clubtails burrowing into sand. Thanks to Marla and Carlos Garrison for sharing these videos via YouTube. Both videos are hyperlinked from “The Search Begins” by Marla Garrison and Ken Tennessen (Argia, Volume 33, Issue 3).
My last blog post was a “sketch pad” of test shots of an exuvia from a Comet Darner dragonfly (Anax longipes) collected by Stanley Caveney on 19 July 2021 from a pond at MeadowWoods in West Elgin, Ontario, Canada. All of the shots in that post are unedited JPGs straight from my camera. This post features edited versions of the RAF (raw) files from that photo shoot, including some images with value-added annotations.
I used Adobe Photoshop to create a composite image that features the best parts of two photos from the sketch pad.
This specimen is from a male Comet Darner, as indicated by its vestigial primary- and secondary genitalia. The inset photo shows a clear view of the vestigial hamuli (secondary genitalia) that are partially obscured in the background photo.
The horn is clearly visible in the last photo. Notice there are three “bumps” located between the eyes of the exuvia: the middle bump is the horn; the antennae bases are located to the left and right of the horn.
If so, then I’m guessing D. transversa larvae are bottom dwellers, as indicated by the dirty, sediment-covered dorsal side and relatively clean ventral side of this specimen.
The nymphs are sprawlers that cling to roots or hunker down in sediments of mixed sand and silt particles. Source Credit: K. J. Tennessen, Dragonfly Nymphs of North America, https://doi.org/10.1007/978-3-319-97776-8_10, Macromiidae, p. 330.
The Backstory
The preceding photos were shot using the prototype for a homemade curved clear plastic tray intended for staging subjects against a white background.
With a few minor tweaks, the curved stage performed better than during initial testing. I needed to add a second external flash unit to more evenly illuminate the white background.
Although I’m fairly satisfied with the results of these test shots, more testing is required to be sure the set-up is working the way I want.
The Common Green Darner dragonfly (Anax junius) exuvia was collected on 17 June 2021 from a small pond at an undisclosed location in Prince William County, Virginia USA.
The Comet Darner dragonfly (Anax longipes) exuvia was collected by Stanley Caveney on 19 July 2021 from a pond at MeadowWoods in West Elgin, Ontario, Canada.
Taxonomy
There are five species of dragonflies in the Genus Anax for the United States and Canada: Amazon Darner (Anax amazili); Common Green Darner (Anax junius); Comet Darner (Anax longipes); Giant Darner (Anax walsinghami); and Blue-spotted Comet (Anax concolor).
Common Green Darner and Comet Darner are the only species from the Genus Anax found where I live in Northern Virginia USA.
This specimen is from Family Aeshnidae (Darners), as indicated by the following field marks: the exuvia has a flat labium that doesn’t cover the face (not mask-like); the antennae are thin and thread-like (not club-like, as in Gomphidae larvae/exuviae); and the eyes are large relative to the size of the head.
Stanley Caveney is shown in the first of several photos taken by Hugh Casbourn. Stan contacted me for confirmation of his tentative identification of several Comet Darner exuviae that he collected during July 2021. Stan kindly gave one of the exuviae to me.
Photo used with written permission from Hugh Casbourn.
I asked Stan whether he had taken photographs of the Comet Darner exuviae in situ. Stan hadn’t, so he and Hugh revisited a local pond where they searched for and found two more exuviae.
How many exuviae do you see in the next photo? Look closely — both cast skins are shown in the same image.
Photo used with written permission from Hugh Casbourn.
An exuvia from a female Comet Darner appears in the foreground of the preceding photograph…
Photo used with written permission from Hugh Casbourn.
and a male Comet Darner appears in the background.
Photo used with written permission from Hugh Casbourn.
I asked Stan for advice regarding where to look for Comet Darner exuviae.
The six exuviae found to date were mainly at the inner edge of the cattail beds, facing the open water of the pond and where the individual cattail plants were spaced out. Source Credit: Personal communication from Stanley Caveney.
Editor’s Note: Sincere thanks to Derek Caveney, Stan’s son, for shipping the exuvia to me. The specimen was packed so carefully that it arrived in excellent condition, as you can see in the first photo in this blog post. I’m looking forward to shooting a complete photo set of the exuvia.
The first individual is a female, as indicated by her mostly yellow coloration and terminal appendages.
17 JUN 2021 | PNC. Wm. County | Yellow-sided Skimmer (female)
Female dragonflies have a pair of cerci (superior appendages) that have little or no function.
Mature male
The last individual is a mature male, as indicated by his light-blue pruinescence and terminal appendages.
17 JUN 2021 | PNC. Wm. County | Yellow-sided Skimmer (male)
Male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”) and a lower unpaired epiproct (“inferior appendage”).
Immature male Yellow-sided Skimmers look similar to females of the same species. Terminal appendages can be used to differentiate the sex of immature males and mature females.
I’m not sure I’d call Black-shouldered Spinyleg a habitat specialist. I’ve seen and photographed D. spinosus along small streams in the forest, mid-size streams (like the one in this post), and large rivers.
Habitat: Rocky and muddy streams and rivers from small to large, more often in woodland. Also in rocky lakes in northern part of range. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 6416-6417). Princeton University Press. Kindle Edition.
Range map
The following map shows all official records for Dromogomphus spinosus in the United States of America. Given the wide range of lotic habitats where Black-shouldered Spinyleg is found, I’m puzzled by the fact that the species isn’t more widespread than it appears to be.
hamules: paired structures that project from genital pocket under second segment and hold female abdomen in place during copulation Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 11618-116198). Princeton University Press. Kindle Edition.
Male dragonfly secondary genitalia, called hamules, are located below abdominal segments two and three (S2 and S3), as shown in the following annotated image. Hamules come in a variety of sizes and shapes, but their function is identical for all species of odonates. Some species of dragonflies and damselflies — such as Ashy Clubtail versus Lancet Clubtail and Southern Spreadwing versus Sweetflag Spreadwing, to name a few — can be differentiated/identified with certainty only by examining the hamules under magnification.
(See a full-size version of the original photo, without annotation.)
Indented hind wings
Male members of many families of dragonflies have “indented” hind wings near the body, with some notable exceptions.
Hind wing venation and shape can identify the sex of most dragonflies. Petaltails, darners (except Anax), clubtails, spiketails, cruisers, and some emeralds. Wing shape isn’t helpful to sex baskettails since they are largely the same. They are different in Cordulia, Dorocordulia, Somatochlora and to a lesser degree, Neurocordulia. Source Credit: Ed Lam, author and illustrator of Damselflies of the Northeast.
Terminal appendages
Identifying female versus male dragonflies and damselflies can be challenging but it’s a little easier when you know how to differentiate their terminal appendages.
