Posts Tagged ‘Family Gomphidae (Clubtails)’

How to estimate instar, revisited

November 16, 2021

I’m the founder and co-administrator of the Odonate Larvae and Exuviae Facebook group. Friday, 12 November 2021 was the two-year anniversary of the group. As of this writing there are approximately 1,700 members in the group, including people from around the world.

For example, Abiodun Matthew Adedapo from Nigeria. Abiodun began posting to the group relatively recently, sharing information and photos related to his research. Sincere thanks to Abiodun for permission to repurpose two of his photos for another mini-lesson on how to estimate instar.

What is the instar? Not F-0.

The equation for instar equivalent is as follows.

Instar equivalent = HwL / HW

Where HwL is Hind wing Length and HW is Head Width.


Photo used with written permission from Abiodun Matthew Adedapo.

I used the Adobe Photoshop “Ruler Tool” to measure the number of pixels along the two double-tipped white arrows shown in the preceding annotated image of a preserved specimen collected and photographed by Abiodun.

HwL is ~132.6 pixels. HW is ~195.12 pixels.

Instar equivalent = 132.6 pixels / 195.12 pixels

The units cancel, so the answer is ~0.68 — close to Ken Tennessen’s  average value for F-1 (final instar minus one).

Abiodun reported the instar as F-2, based upon in situ observations of a cohort of larvae (nymphs) from Family Gomphidae (Clubtails).

For my purpose, it doesn’t matter whether the actual instar is either F-1 or F-2 — the important take-away is we know the instar is not F-0, the final instar. This provides an opportunity to mention a simpler way to estimate final instar.

Larvae in the final stage can be recognized by the length of the wing buds which cover the fourth abdominal segment. Source Credit: Field Guide to the larvae and exuviae of British Dragonflies, by Steve Cham, p. 30.

Look closely at the first annotated image. Notice the length of the wing buds/pads doesn’t reach the fourth abdominal segment (S4) of the specimen therefore this larva is not in its final instar.

Thanks to Freda van den Broek for sharing this method with me!

F-0 (final instar)

The last annotated image shows part of a different larva also collected and photographed by Abiodun. Notice the length of the wing buds/pads does reach S4, therefore this larva is in its final instar.

Photo used with written permission from Abiodun Matthew Adedapo.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Anal pyramid

October 26, 2021

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.



The Backstory

The Eastern Ringtail dragonfly (Erpetogomphus designatus) exuvia shown above was collected along the Potomac River at Riverbend Park, Fairfax County, Virginia USA. This species is a member of Family Gomphidae (Clubtails). I created a photo-illustrated identification guide for E. designatus using the same specimen.

Copyright © 2021 Walter Sanford. All rights reserved.

Burrowing hooks

October 12, 2021

Odonate nymphs (larvae) can be classified broadly into three (3) groups: Burrowers; Climbers/Clingers; and Sprawlers. Source Credit: “Conservation of Illinois: Dragonflies” Webinar (1:17:19) by Marla Garrison, McHenry County College.

Some species of 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.

Pop Quiz: Using the preceding annotated image as a guide, can you find the burrowing hooks on the front- and middle legs of the following specimen?

Related Resources

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).

Common Sanddragon (Progomphus obscurus)

Riverene Clubtail (Stylurus amnicola)

Copyright © 2021 Walter Sanford. All rights reserved.

Previews of Coming Attractions – Fall Species of Odonates

August 31, 2021

There is an annual cycle of odonate activity that can be subdivided into three broad categories: Early Season (spring); Mid-season (summver); and Late Season (fall).

As we endure the “Dog Days of Summer,” waiting for the calendar to turn to fall, it’s time to begin looking for the Late Season (fall) species of odonates.

This blog post provides a photo sampler of some of the fall species of odonates that can be seen during September, October, and November in the Commonwealth of Virginia. This post is not intended to be a comprehensive field guide that features every odonate species that can be seen during the same time period.

Full Disclosure

Some fall species are easier to find than others. And some species are flyers rather than perchers, making it almost essential to capture them in flight using an insect net. That being said, it’s richly rewarding to find any of the rare to uncommon species so do your homework and be persistent. Good luck and happy hunting!

Editor’s Notes

Click on the date listed in the caption for each photo to see the original blog post for that image; click on the odonate name to see all of my blog posts related to that species.

Sincere thanks to Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, for providing photographs of many of the rare to uncommon fall species of odonates featured in this photo sampler. Click on the word “Photo” in the caption for each of Mike’s photographs to see his original Facebook post for that image.

Every species features the following information: common name; scientific name; early-date/late-date; abundance; and habitat. All information is excerpted from “CHECKLIST OF THE DRAGONFLIES AND DAMSELFLIES OF VIRGINIA, April 2017 and April 2020 updates” by Dr. Steve Roble, Staff Zoologist at the Virginia Department of Conservation and Recreation, Division of Natural Heritage.

Dragonflies (Order Anisoptera)

Family Aeshnidae (Darners)

Black-tipped Darner (Aeshna tuberculifera)

Adult flight period: JUN 30 – OCT 29. Rare to uncommon. Habitat: Montane ponds.

Photo used with written permission from Michael Boatwright.

Common Green Darner (Anax junius)

Adult flight period: FEB 27 – DEC 30. Common. Habitat: Ponds.

Fawn Darner (Boyeria vinosa)

Adult flight period: JUN 03 – NOV 07. Common. Habitat: Streams, rivers.

Shadow Darner (Aeshna umbrosa)

Adult flight period: JUN 08 – DEC 05. Common. Habitat: Ponds, streams.

Family Corduliidae (Emeralds)

Clamp-tipped Emerald (Somatochlora tenebrosa)

Adult flight period: JUN 08 – OCT 15. Common. Habitat: Ponds, small streams.

Photo used with written permission from Michael Boatwright.

Fine-lined Emerald (Somatochlora filosa)

Adult flight period: JUL 10 – OCT 15. Rare to uncommon. Habitat: Boggy streams, swamps, marshes.

18 SEP 2019 | PNC. Wm. County | Fine-lined Emerald (male)

Family Gomphidae (Clubtails)

Arrow Clubtail (Stylurus spiniceps)

Adult flight period: JUN 13 – OCT 19. Uncommon to common. Habitat: Rivers.

Photo used with written permission from Michael Boatwright.

Laura’s Clubtail (Stylurus laurae)

Adult flight period: JUN 20 – SEP 26. Rare to uncommon. Habitat: Streams, rivers.

Photo used with written permission from Michael Boatwright.

Russet-tipped Clubtail (Stylurus plagiatus)

Adult flight period: JUN 15 – NOV 06. Uncommon to common. Habitat: Streams, rivers.

Family Libellulidae (Skimmers)

Autumn Meadowhawk (Sympetrum vicinum)

Adult flight period: MAY 28 – JAN 03. Common. Habitat: Ponds.

Blue-faced Meadowhawk (Sympetrum ambiguum)

Adult flight period: MAY 22 – NOV 19. Uncommon. Habitat: Swamps, ponds.

Black Saddlebags (Tramea lacerata)

Adult flight period: APR 12 – OCT 30. Common. Habitat: Ponds.

(See a full-size version of the original photo, without annotation.)

Spot-winged Glider (Pantala hymenaea)

Adult flight period: MAY 08 – OCT 20. Common. Habitat: Ponds.

A Spot-winged Glider dragonfly (Pantala hymenaea) netted at Saint Louis Catholic School, Fairfax County, Virginia USA. This individual is a female.

20 JUL 2016 | Fairfax County, VA USA | Spot-winged Glider (female)

Wandering Glider (Pantala flavescens)

Adult flight period: MAY 02 – NOV 17. Common. Habitat: Ponds.

Damselflies (Order Zygoptera)

Family Lestidae (Spreadwings)

Great Spreadwing (Archilestes grandis)

Adult flight period: JUN 25 – NOV 11. Uncommon. Habitat: Streams, ponds.

Spotted Spreadwing (Lestes congener)

Adult flight period: JUN 10 – NOV 11. Uncommon. Habitat: Ponds.

Photo used with written permission from Michael Boatwright.


Classification of Fall Species into Sub-groups

Migratory Species

At least five major species of dragonflies known to be migratory in North America.

  • Black Saddlebags (Tramea lacerata)
  • Common Green Darner (Anax junius)
  • Spot-winged Glider (Pantala hymenaea)
  • Wandering Glider (Pantala flavescens)

Rare to Uncommon Species

  • Arrow Clubtail (Stylurus spiniceps)
  • Black-tipped Darner (Aeshna tuberculifera)
  • Blue-faced Meadowhawk (Sympetrum ambiguum)
  • Clamp-tipped Emerald (Somatochlora tenebrosa)
  • Fine-lined Emerald (Somatochlora filosa)
  • Laura’s Clubtail (Stylurus laurae)
  • Ocellated Darner (Boyeria grafiana)
  • Great Spreadwing (Archilestes grandis)
  • Spotted Spreadwing (Lestes congener)

Copyright © 2021 Walter Sanford. All rights reserved.

Black-shouldered Spinyleg (female)

August 13, 2021

A Black-shouldered Spinyleg dragonfly (Dromogomphus spinosus) was spotted by Michael Powell during a photowalk with me along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

This individual is a female, as indicated by her rounded hind wings and terminal appendages.

05 AUG 2021 | PNC. Wm. County | Black-shouldered Spinyleg (female)

We followed the female from one location…

05 AUG 2021 | PNC. Wm. County | Black-shouldered Spinyleg (female)

to another.

05 AUG 2021 | PNC. Wm. County | Black-shouldered Spinyleg (female)

I was able to take no more than three shots at each perch before she moved on to the next stop.

05 AUG 2021 | PNC. Wm. County | Black-shouldered Spinyleg (female)


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.

Related Resource: All posts in my blog tagged with the words “Black-shouldered Spinyleg dragonfly.”

Copyright © 2021 Walter Sanford. All rights reserved.

Post update: Stylurus sp. exuvia

July 27, 2021

Three years ago I had the honor and pleasure of helping Michael Boatwright, my good friend and odonate hunting buddy, identify an interesting exuvia that he collected on 13 July 2018 at an undisclosed location in Amherst County, Virginia USA.

After working through several dichotomous keys for the identification of odonate larvae/exuviae, Mike and I determined the specimen is most likely from Zebra Clubtail (Stylurus scudderi). Zebra Clubtail is extremely rare in the state of Virginia.

The following annotated image shows a dorsal view of the exuvia.

13 JUL 2018 | Amherst County, VA USA | Stylurus scudderi (exuvia)

The best way to confirm our tentative identification of the exuvia is to find adult Zebra Clubtail at the same location. Easier said than done! During the next few years, Mike found more exuviae but no adults.

On 22 July 2021, years of searching the site finally came to fruition when Mike discovered a teneral female Zebra Clubtail, shown below.

Photo used with written permission from Mike Boatwright.

Look closely at the full-size version of the preceding photo. Notice the teneral dragonfly is perched on the exuvia from which it emerged. Mike collected the exuvia after the dragonfly flew high into the tree canopy, so now we have the type specimen for verification of other exuviae.

Persistence pays

Sincere congratulations, Mike! You never gave up when it would have been the easier thing to do.

Related Resources

  • Stylurus sp. exuvia – a blog post by Walter Sanford providing a detailed account of the process used to determine the identity of the specimen collected by Mike on 13 July 2018.
  • Mike’s post in the Virginia Odonata Facebook group announcing his discovery on 22 July 2021. Mike is the founder and administrator of Virginia Odonata.

Copyright © 2021 Walter Sanford. All rights reserved.

Common Sanddragon dragonflies (males)

July 2, 2021

Two Common Sanddragon dragonflies (Progomphus obscurus) were spotted along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

Both individuals are male, as indicated by their terminal appendages and “indented” hind wings.

Male No. 1

I spotted a Common Rockdragon while searching for Eastern Least Clubtail (Stylogomphus albistylus). OK, OK, there is no species of dragonfly called “Common Rockdragon.” My point is simply this: Common Sanddragon is typically found perching on sand rather than rocks. Any perch in a storm I guess.

17 JUN 2021 | PNC. Wm. County | Common Sanddragon (male)

Anyway, this guy was super skittish — I got one shot before he flew away. I waited a while for him to return. No luck. So I moved on.

Male No. 2

I stopped to rest at a sandy bank (located farther upstream from the first location)  where I have seen/photographed Common Sanddragon in the past. Sure enough, a male Common Sanddragon landed on the beach soon after I sat down on my camp stool.

The first photo is cropped for better composition.

17 JUN 2021 | PNC. Wm. County | Common Sanddragon (male)

He took flight several times but always returned to the same place. I speculate he was actively hunting insects flying over the stream.

The next two photos are full-frame (4,000 x 3,000 pixels), that is, uncropped.

17 JUN 2021 | PNC. Wm. County | Common Sanddragon (male)

The male’s “indented” hind wings (see “Related Resource”) are shown clearly in the full-size versions of these photos.

17 JUN 2021 | PNC. Wm. County | Common Sanddragon (male)

Related Resource

Ed Lam, author and illustrator of Damselflies of the Northeast, created the following composite image that shows how to differentiate male and female Common Sanddragons. Notice the difference in the shape of male and female hind wings: male hind wings are “indented” near the body; female hind wings are rounded.


Copyright © 2021 Walter Sanford. All rights reserved.

Unicorn Clubtail dragonfly (male)

June 29, 2021

A Unicorn Clubtail dragonfly (Arigomphus villosipes) was photographed near the shoreline of a small pond at an undisclosed location in Fairfax County, Virginia USA.

This individual is a male, as indicated by his terminal appendages. 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”).

For those of you keeping score at home, notice male Unicorn terminal appendages have four points/prongs. Does that mean A. villosipes is an exception to the rule of three terminal appendages for male dragonflies? In a word, no.

05 JUN 2021 | Fairfax County, VA | Unicorn Clubtail (male)

The preceding photo shows a clear view of the male’s terminal appendages. Zoom-in on the full-size version of the photo and you should notice that the epiproct for Unicorn Clubtail is essentially a wide plate with two points/prongs.

Related Resource: Odonate Terminal Appendages – a permanent reference page in my blog featuring identification guides for most of the common species of odonates found in Virginia, and even some of the uncommon to rare species.

Copyright © 2021 Walter Sanford. All rights reserved.


Ashy Clubtail dragonfly (male)

May 28, 2021

An Ashy Clubtail dragonfly (Phanogomphus lividus) was spotted during a photowalk with Michael Powell along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

13 MAY 2021 | Prince William County, VA | Ashy Clubtail (male)

This individual is a male, as indicated by his terminal appendages. A dorsal view of the same species shows the hind wings of Ashy males are “indented.” The male was perched on rocks, sand, and leaf litter deposited along the edges of the stream channel.

13 MAY 2021 | Prince William County, VA | Ashy Clubtail (male)

I’ve seen Ashy Clubtail dragonflies many times, but this was the first time I noticed their unusual flight pattern. Imagine a one-car roller coaster, going up and down smoothly while moving forward slowly. That’s the best way I can describe what I saw. You’ll recognize it when you see it — very distinctive!

My buddy Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, told me Lancet Clubtail (Phanogomphus exilis) has the same flight pattern.

Tech Tips

Both photos are full-frame (4,000 x 3,000 pixels), that is, uncropped. I considered cropping the photos to make the dragonfly appear larger. I decided to post the uncropped photos to show the smallish size of Ashy Clubtail more authentically. Click on each photo in order to see a full-size version that you can zoom-in on to see more detail.

Copyright © 2021 Walter Sanford. All rights reserved.

Dromogomphus spinosus exuvia (dorsal view)

February 19, 2021

Gomphidae (Clubtails) is the second largest family of dragonflies, behind Libellulidae (Skimmers). Many types of clubtail larvae (nymphs)/exuviae look similar, adding to the challenge of identifying some specimens to the genus and species level.

This specimen has a flat labium that doesn’t cover the face (not mask-like), indicating it’s either Aeshnidae (Darners) or Gomphidae; the shape of the body suggets Gomphidae. Several more field marks can be used to identify this specimen as a Black-shouldered Spinyleg (Dromogomphus spinosus) exuvia.

16 FEB 2021 | BoG Photo Studio | D. spinosus exuvia (dorsal)

The specimen is approximately 3.3 cm (~1.3 in) long, measured from head to tail. Notice the mid-dorsal hooks/spines located along the abdomen of the body.

At first I thought the exuvia might be a species from the genus Stylurus, based upon the mid-dorsal spine on abdominal segment nine (S9). After careful examination of two excellent photo-illustrated PowerPoint presentations by Kevin Hemeon at NymphFest 2016 (see Related Resources, below), I noticed none of the species in the genus Stylurus have dorsal hooks. That’s when I realized the specimen must be D. spinosus. Eureka! Source Credit: Dromogomphus spinosus exuvia – a blog post published on 28 June 2019 by Walter Sanford.

Related Resources

The following PowerPoint presentations by Kevin Hemeon are available in the “Files” section of the Northeast Odonata Facebook group. Direct links to the documents are provided below.

Odonate Exuviae – a hyperlinked list of identification guides to many species of odonate exuviae from seven families of dragonflies and three families of damselflies.

Tech Tips

The photograph featured in this blog post is a “one-off,” that is, a single photo rather than a focus-stacked composite image. The camera lens was set for f/16; the camera body was set for ISO 160 and a shutter speed of 1/250 s.

The photo was taken using a Fujifilm X-T3 digital camera, Fujifilm MCEX-11 extension tube, Fujinon XF80mm macro lens (120mm, 35mm equivalent), and an array of external lights.

Two external flash units were used to create the white background by cross lighting the front of a piece of white plastic; another flash was used to light the subject. A Sunpack LED 160 was used as a focusing aid.

RAW FILE CONVERTER EX 3.0 was used to convert one RAW (RAF) file to a TIFF file. The TIFF file was edited using Apple Aperture and sharpened using Photoshop.

Copyright © 2021 Walter Sanford. All rights reserved.

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