Epitheca princeps exuvia

An odonate exuvia was collected by Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, on 07 June 2018 at Otter Lake in Amherst County, Virginia USA.

A two-step process was used to identify the genus and species of the specimen.

1. Determine the family.
2. Determine the genus and species.

Step 1. Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video, Identifying dragonfly larva to family (8:06). Here’s the decision tree used to identify the exuvia as a member of the Family Corduliidae (Emeralds).

• The specimen has a mask-like labium (prementum) that covers the face, as shown in Image No. 1, characteristic of four families of odonates: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
• There is no horn on the face-head, characteristic of Macromiidae, so it’s not a cruiser.
• Cordulegastridae has jagged crenulations on its labium, so it’s not a spiketail. The crenulations for Corduliidae and Libellulidae look similar.
• Look at the anal pyramid to differentiate Corduliidae and Libellulidae: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts, as shown in Image No. 4. [Editor’s Note: It’s probably Libellulidae if the cerci are less than half the length of the paraprocts.]

In summary, the exuvia has a mask-like labium with relatively smooth crenulations, no horn on its face-head, and the cerci are more than half as long as the paraprocts, confirming that the specimen is a member of Family Corduliidae (Emeralds).

No. 1 | Epitheca princeps | exuvia (face-head)

Step 2. Genus and species

Characters from two dichotomous keys were used to identify the genus and species: Prince Baskettail dragonfly (Epitheca princeps). See Epitheca princeps exuvia, another of my illustrated guides to identification of odonate exuviae, for a detailed explanation of the decision tree used to identify the genus and species of this specimen.

No. 2 | Epitheca princeps | exuvia (dorsal)

This individual is a male, as indicated by the vestigial hamuli visible on the ventral side of abdominal segments two and three (S2-3).

No. 3 | Epitheca princeps | exuvia (ventral)

Notice the cerci are at least half as long as the paraprocts, as shown in Image No. 4.

No. 4 | Epitheca princeps | exuvia (posterior abdomen)

Image No. 5 shows a dorsal-lateral view of the mid-dorsal hooks.

No. 5 | Epitheca princeps | exuvia (dorsal-lateral)

Look-alike species

I really wanted this specimen to be Stream Cruiser dragonfly (Didymops transversa). I think exuviae from D. transversa and E. princeps are similar in appearance — an opinion not shared by at least one expert on identification of odonate exuviae.

Two characters proved to be the deal-breaker that forced me to abandon D. tranversa in favor of E. princeps. 1) The specimen does not have a horn on its face-head. 2) This specimen is only 25 mm long (2.5 cm); D. transversa larvae/exuviae are 30 mm long (3.0 cm), according to Dragonflies of North America, Needham, James G., et al.

Tech Tips

The following equipment was used to shoot Image No. 1-5: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tube; Canon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode.

Image No. 1-5 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017: Image No. 1 (7 photos); Image No. 2 (22 photos); Image No. 3 (19 photos); Image No. 4 (10 photos); Image No. 5 (20 photos).

Copyright © 2018 Walter Sanford. All rights reserved.

Green-eyed Stream Cruiser

A Stream Cruiser dragonfly (Didymops transversa) was spotted during a photowalk along a mid-size stream in Fairfax County, Virginia USA. This individual is a male, as indicated by his terminal appendages and indented hind wings.

03 MAY 2017 | Fairfax County, VA | Stream Cruiser (male)

Male: Eyes brown with green highlight above. … Female: Eyes brown. Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 7192, 7194-7195). Princeton University Press. Kindle Edition.

I’ve never seen a green-eyed Stream Cruiser like this one — every one had brown eyes, including both males and females.

Copyright © 2017 Walter Sanford. All rights reserved.

Stream Cruiser dragonfly (male)

Another Stream Cruiser dragonfly (Didymops transversa) was spotted during a photowalk along Beaver Pond Loop Trail at Accotink Bay Wildlife Refuge, Fairfax County, Virginia USA.

10 APR 2017 | Accotink Bay Wildlife Refuge | Stream Cruiser (male)

This individual is a male, as indicated by his “indented” hind wings and terminal appendages.

10 APR 2017 | Accotink Bay Wildlife Refuge | Stream Cruiser (male)

Stream Cruiser dragonflies typically perch at a 45° angle because of their extremely long legs, especially noticeable in the last photo.

For another perspective on the same male, both literally and figuratively, see Stream Cruiser dragonfly by fellow photoblogger Michael Powell.

Copyright © 2017 Walter Sanford. All rights reserved.

Stream Cruiser dragonfly (female)

A Stream Cruiser dragonfly (Didymops transversa) was spotted during a photowalk along Beaver Pond Loop Trail at Accotink Bay Wildlife Refuge, Fairfax County, Virginia USA.

10 APR 2017 | Accotink Bay Wildlife Refuge | Stream Cruiser (female)

This individual is a female, as indicated by her rounded hind wings and terminal appendages. Look closely at the face and head of the dragonfly. Can you see why “ice cream sandwich face” is my nickname for Stream Cruiser?

The female landed long enough for me to shoot four photos before she flew away — not enough time for me to point her out to Michael Powell, a fellow amateur wildlife photographer and blogger who joined me in search of his first Stream Cruiser. Fortunately, Mike and I were able to photograph a male Stream Cruiser later the same afternoon. Look for photos of the male in my next blog post.

Addendum

I cropped the photo into a square format in order to remove a distracting element. Can you tell what I dislike about the original version? I prefer the square format. Which version do you prefer?

10 APR 2017 | Accotink Bay Wildlife Refuge | Stream Cruiser (female)

Copyright © 2017 Walter Sanford. All rights reserved.

Another female Stream Cruiser?

It’s possible the female Stream Cruiser dragonfly (Didymops transversa) in this gallery — spotted on 20 April 2016 at Accotink Bay Wildlife Refuge — is the same individual featured in a photoblog post published on 23 April 2016.

This is the second photo set that I shot of female Stream Cruisers spotted along the same segment of Beaver Pond Loop Trail. Although the two female dragonflies were perching on opposite sides of the trail, this female could be the same one that I spooked a few minutes earlier when I moved too close for her comfort.

This individual is a female as indicated by the pair of white terminal appendages (cerci) at the end of her abdomen, clearly visible in the following photo.

Stream Cruiser dragonflies have extremely long legs, especially noticeable in the last photo. The abdomen of female Stream Cruisers is thicker than males of the same species, similar to many species of odonates.

Copyright © 2016 Walter Sanford. All rights reserved.

Stream Cruiser dragonflies (males)

Several male Stream Cruiser dragonfly (Didymops transversa) were spotted on 20 April 2016 at Accotink Bay Wildlife Refuge.

All male dragonflies have three terminal appendages: two (2) cerci; and one (1) epiproct. All three appendages are white. Male Stream Cruiser cerci are shaped differently than female cerci: male cerci look like a pair of ivory elephant tusks.

No. 1

No. 2

If you look closely at the full-size version of the following photo, then you will notice the focus is slightly “soft.” Here’s the backstory. I waited nearly 30 minutes for this male to land in a spot where I could shoot its photo. When the dragonfly finally landed, I positioned my Coleman camp stool at a distance of approximately six feet from the subject: the dragonfly was perching on one side of a trail; I was sitting on the other side. As soon as I shot the first photo, I noticed a family of four plus a BIG dog approaching my position rapidly. I rushed to take a second shot, in case the group didn’t stop. They didn’t stop — they charged ahead, passing between the dragonfly and me. I never saw the same dragonfly again.

So what’s the take-away from this negative experience? The people must have noticed that I was trying to photograph something, yet they didn’t stop and ask whether it would be OK to pass by. If they had, then I would have asked them to indulge me for a few minutes so I could shoot a few more photos. Don’t be like these people — please be considerate of photographers that you encounter, especially wildlife photographers!

No. 3

The last photo in this set is my favorite. It’s tack-sharp and the palette of background colors complements the coloration of the dragonfly. I love it when a plan comes together!

Copyright © 2016 Walter Sanford. All rights reserved.

Stream Cruiser dragonfly (female)

The following photograph shows a Stream Cruiser dragonfly (Didymops transversa) spotted on 20 April 2016 as I was photowalking along a trail at Accotink Bay Wildlife Refuge.

Key field markers for Didymops transversa include a white facial bar and a single white stripe on the side of the thorax. Male– and female Stream Cruisers are similar in appearance. This individual is a female as indicated by the pair of white terminal appendages (cerci) clearly visible at the end of her abdomen.

I shot lots of photos of this individual, including many good- to very good shots. This image is one of my favorites. When editing photographs of dragonflies that like to perch in places where the background is cluttered, usually it is necessary to crop the original image. Not this photo — it is uncropped because the subject fills the frame and the composition looks good as is.

I plan to post more photos of Stream Cruiser dragonflies, including this female as well as several males spotted on the same day.

Copyright © 2016 Walter Sanford. All rights reserved.

Can I see some eye-dentification?

It may seem like all dragonflies look alike when you’re beginning to learn how to identify dragonflies. For example, all dragonflies have large, multifaceted compound eyes. Look closely. Careful observation of the color, shape, and size of eyes should enable you to quickly identify the family (or families) of dragonflies to which a specimen may belong.

The following field markers — used in combination with a good field guide to dragonflies, a species list for your location, and the process of elimination — should enable you to identify unknown specimens more quickly than randomly trying to find a match between your specimen and one of the 316 of species of dragonflies known to occur in the United States!

Clubtail Family (and Petaltail Family)

The eyes of clubtail dragonflies (and petaltails) are widely separated, somewhat similar to the eyes of damselflies. The Clubtail Family is the second largest family of dragonflies, so this field marker should be useful for identifying a lot of dragonflies to the family level — if only clubtails were as easy to identify down to the species level!

09 MAY 2013 | Meadowood Recreation Area | Ashy/Lancet Clubtail (female)

The preceding dragonfly is either an Ashy Clubtail (Gomphus lividus) or Lancet Clubtail (Gomphis exilis). Ashy- and Lancet Clubtail dragonflies are similar in appearance and difficult to differentiate with complete certainty. But one look at those eyes and you know it’s definitely some species of clubtail!

Spiketail Family

Notice the eyes of the following dragonfly nearly touch at a point between its eyes — that’s a distinctive field marker for the Spiketail Family.

09 MAY 2013 | Meadowood Recreation Area | Brown Spiketail (female)

Cruiser, Emerald, and Skimmer Families

In a few families of dragonflies, the eyes meet along a short seam near the face.

The Skimmer Family is the largest family of dragonflies. Many species of Skimmers are common and fairly easy to identify.

There are fewer species of dragonflies in the Cruiser Family than the Skimmer Family; no other dragonflies in the United States look similar to cruisers.

02 MAY 2013 | Accotink Bay Wildlife Refuge | Stream Cruiser (male)

Many species of the Emerald Family feature distinctive bright green eyes, hence the family name.

25 JUL 2012 | The Wildlife Sanctuary | Mocha Emerald (male)

Darner Family

The eyes of Darners meet along a long seam from front-to-back.

14 AUG 2012 | Huntley Meadows Park | Common Green Darner (mating pair)

Self-test

OK, let’s apply what you just learned. Looking at the eyes only, can you identify the family for the following dragonfly? If you would like to know whether your answer is correct, then please leave a comment.

Teacher’s Note: In order to avoid revealing the answer to the one-question quiz as soon as the first person comments, I changed the settings for this blog so that comments must be approved manually.

26 JUN 2015 | Wickford Park | [Insert family name here.]

Editor’s Notes: This post is adapted from Dragonfly Head & Eyes, one of many excellent guides on the Odes for Beginners Web site. Thanks for the inspiration, Sheryl Chacon!

Copyright © 2015 Walter Sanford. All rights reserved.

A sampler of male dragonfly claspers (Part 1)

All 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”). Claspers come in a variety of shapes and sizes, but their function is identical for all species of dragonflies.

There are seven families of dragonflies. Part 1 (of 2) features a sampler of select images showing male dragonfly claspers from the Clubtail Family, Cruiser Family, and Darner Family.

Clubtail Family

The following image shows a male Ashy Clubtail dragonfly (Gomphus lividus) perching on the ground in a field located near Giles Run at Meadowood Recreation Area in Fairfax County, Virginia.

02 MAY 2014 | Meadowood Recreation Area | Ashy Clubtail (male)

Cruiser Family

The next image shows a male Stream Cruiser dragonfly (Didymops transversa) spotted along “Beaver Pond Loop Trail” at Accotink Bay Wildlife Refuge, a 1,200 acre preserve located at Army Garrison Fort Belvoir, Fairfax County, Virginia.

02 May 2013 | Accotink Bay Wildlife Refuge | Stream Cruiser (male)

Darner Family

The last image shows a male Shadow Darner dragonfly (Aeshna umbrosa) spotted near a vernal pool in the forest at Huntley Meadows Park.

24 OCT2014 | Huntley Meadows Park | Shadow Darner (male)

Related Resources:

• Dragonfly terminal appendages (male, female) [Painted Skimmer]
• More dragonfly terminal appendages [Blue-faced Meadowhawk]
• A sampler of male dragonfly claspers (Part 2)
• Odonate Terminal Appendages

Editor’s Notes: Part 2 (of 2) will feature a sampler of select images showing male dragonfly dragonfly claspers from the Emerald Family, Skimmer Family, and Spiketail Family. The author never has been fortunate to photograph either species of the Petaltail Family.

Copyright © 2015 Walter Sanford. All rights reserved.

Stream Cruiser dragonfly (female)

The following photograph shows a Stream Cruiser dragonfly (Didymops transversa) spotted as I was photowalking along a dirt trail at Meadowood Recreation Area on 08 May 2014.

Male– and female Stream Cruisers are very similar in appearance: a white facial bar and a single white stripe on the side of the thorax are key characteristics of Didymops transversa. This individual is a female as indicated by the pair of white terminal appendages (cerci) clearly visible at the end of its abdomen.

Thanks to Mr. Chris Hobson, Natural Areas Zoologist with the Virginia Natural Heritage Program, Virginia Department of Conservation and Recreation, for providing species descriptors paraphrased in this post.

Copyright © 2014 Walter Sanford. All rights reserved.