Archive for February, 2020

MYN – Stylurus plagiatus exuvia

February 28, 2020

A Russet-tipped Clubtail dragonfly (Stylurus plagiatus) exuvia was collected by Joe Johnston on 17 July 2019 along Aquia Creek in Stafford County, Virginia USA.

17 JUL 2019 | Aquia Creek | Stylurus plagiatus | exuvia (face-head)

Notice the specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in the preceding photo. This field mark indicates the exuvia is from either Family Aeshnidae (Darners) or Family Gomphidae (Clubtails). Other field marks, including club-like antennae and the shape of the body, indicate this individual is a species of clubtail.

My next blog post will feature a dorsal-lateral view of the exuvia that clearly shows the field marks that indicate both genus and species.

Related Resources

Tech Tips

This specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique. I used the new variation on my old MYN studio rig and I’m still satisfied with the results.

Copyright © 2020 Walter Sanford. All rights reserved.

MYN – Unknown dragonfly exuvia (redux)

February 26, 2020

This blog post features more photos of an exuvia from an unknown species of odonate that was collected by Joe Johnston on 07 August 2019 along Aquia Creek at Channel Marker No. 34, Stafford County, Virginia USA.

The specimen is probably from either Family Corduliidae (Emeralds) or Family Libellulidae (Skimmers).

07 AUG 2019 | Aquia Creek | dragonfly exuvia (dorsal view)

The rule of thumb for differentiating Corduliidae exuviae from Libellulidae is as follows: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts; it’s probably Libellulidae if the cerci are less than half the length of the paraprocts.

07 AUG 2019 | Aquia Creek | dragonfly exuvia (ventral view)

I’m having a hard time seeing the cerci clearly. If I’m seeing what I think I’m seeing, then the cerci are at least half as long as the paraprocts and the exuvia is from Family Corduliidae (Emeralds).

In order to verify my tentative identification, I need to use a higher magnification macro lens (such as my Canon MP-E 65mm Macro lens) in order to shoot a close-up view of the anal pyramid/terminal appendages (see inset diagram, lower-left corner).

Related Resource: MYN – Dragonfly exuvia (unknown species)

Tech Tips

This specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique. I used the new variation on my old MYN studio rig and I’m still satisfied with the results.

Copyright © 2020 Walter Sanford. All rights reserved.

MYN – Dragonfly exuvia (unknown species)

February 24, 2020

An exuvia from an unknown species of odonate was collected by Joe Johnston on 07 August 2019 along Aquia Creek at Channel Marker No. 34, Stafford County, Virginia USA.

The specimen is definitely a dragonfly, probably from either Family Corduliidae (Emeralds) or Family Libellulidae (Skimmers).

07 AUG 2019 | Aquia Creek | dragonfly exuvia (face-head-dorsal view)

This relatively small exuvia is ~1.2 to 1.3 cm in length. Notice the dorsal hooks on the exuvia are “cultriform,” that is, shaped like a pruning knife.

07 AUG 2019 | Aquia Creek | dragonfly exuvia (lateral view)

Related Resource: Odonate exuviae collecting sites [along Aquia Creek]

Tech Tips

This specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique.

I experimented with a new variation on my old MYN studio rig. The new set-up seems to work well, although the question remains “Does it work well consistently?” I added a second external flash unit that is used to backlight a piece of translucent white plastic (the background), and I physically separated the clear plastic “stage” from the white background. More info and photos will be featured in a follow-up blog post.

Copyright © 2020 Walter Sanford. All rights reserved.

MYN – Clubtail exuvia (possible G. vastus)

February 21, 2020

An odonate exuvia was collected from the concrete boat ramp at Riverbend Park, Fairfax County, Virginia USA. This individual is a member of Family Gomphidae (Clubtails), possibly Cobra Clubtail (Gomphurus vastus).

The specimen was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique.

The first photograph was especially challenging to shoot. The camera viewpoint and the beam of light used to backlight the “stage” were at a nearly 90° angle, relative to each other, with the net result that the light level fell below pure white toward the background. The work-around that I used is less than elegant and needs to be refined. Any suggestions?

27 MAY 2017 | Riverbend Park | Clubtail exuvia (face-head-dorsal view)

Although the next photo appeared in my last blog post, this version was rotated slightly for a more pleasing appearance than the last iteration.

27 MAY 2017 | Riverbend Park | Clubtail exuvia (dorsal view)

The last photo is focused on the thorax in order to provide a relatively clear view of the prementum. Notice the specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in the first photo. This field mark indicates the exuvia is from either Family Aeshnidae (Darners) or Family Gomphidae (Clubtails). Other field marks, including club-like antennae and the shape of the body, indicate this individual is a species of clubtail.

27 MAY 2017 | Riverbend Park | Clubtail exuvia (ventral view)

Related Resource: Gomphurus vastus exuvia, an identification guide by Walter Sanford featuring annotated images.

Copyright © 2020 Walter Sanford. All rights reserved.

MYN – Clubtail exuvia (dorsal)

February 19, 2020

An odonate exuvia was collected from the concrete boat ramp at Riverbend Park, Fairfax County, Virginia USA. This individual appears to be a member of Family Gomphidae (Clubtails), possibly Cobra Clubtail (Gomphurus vastus).

27 MAY 2017 | Riverbend Park | Clubtail exuvia (dorsal view)

The specimen was photographed against a pure white background using the “Meet Your Neighbours” (MYN) technique.

Related Resource: Gomphurus vastus exuvia, an identification guide by Walter Sanford featuring annotated images.

Copyright © 2020 Walter Sanford. All rights reserved.

MYN – Cicada exuvia

February 17, 2020

An Annual/Periodical Cicada (Family Cicadidae) exuvia was collected from a wooden kayak rack near the concrete boat ramp at Riverbend Park, Fairfax County, Virginia USA.

The specimen was photographed against a pure white background using the “Meet Your Neighbours” (MYN) technique.

27 MAY 2017 | Riverbend Park | cicada exuvia (face-head-dorsal)

Notice the proboscis between the cicada’s two large front legs, as shown in the preceding photo. I’ve seen zillions of cicada exuviae but never noticed a proboscis. Macro photography. It’s good thing!

27 MAY 2017 | Riverbend Park | cicada exuvia (dorsal view)

27 MAY 2017 | Riverbend Park | cicada exuvia (dorsallateral view)

27 MAY 2017 | Riverbend Park | cicada exuvia (dorsallateral view)

The proboscis is plainly visible in the following photo. (Look between the base of the two front legs.)

27 MAY 2017 | Riverbend Park | cicada exuvia (ventral view)

In situ Photographs

Which photo set do you thinks looks more interesting, the Meet Your Neighbours style photographs or the more traditional style of nature photography? In my opinion, the winner is clear!

Related Resources

What are the take-aways?

Based upon the table of “broods” featured in the Wikipedia page listed under Related Resources, I’m thinking the cicada exuvia that I collected during 2017 is more likely an annual cicada than a periodical cicada. For what it’s worth, no evidence of a mass emergence of cicadas was observed.

Copyright © 2020 Walter Sanford. All rights reserved.

What is it?

February 14, 2020

Ladies and gentlemen, boys and girls, children of all ages — it’s time for another exciting episode of “What is it?” Well, what is shown in the following photograph? If you think you know what it is, then please leave a comment. The answer will be provided in a post update.

27 MAY 2017 | Riverbend Park | What is it?

Post Update: Behold the humble cicada exuvia!

Copyright © 2020 Walter Sanford. All rights reserved.

Sexing odonate exuviae (Zygoptera)

February 12, 2020

For some (but not all) species of odonate larvae/exuviae, sex is indicated by either a rudimentary ovipositor (female) or vestigial genitalia (male). These sex organs don’t look exactly the same for all species of damselflies, but their function is identical.

The following photo gallery shows relatively clear examples that illustrate how to sex odonate exuvia in Suborder Zygoptera (Damselflies).

Female (rudimentary ovipositor)

Family Calopterygidae (Broad-winged Damselflies)

(none)

Family Coenagrionidae (Narrow-winged Damselflies)

11 MAR 2017 | Argia sp. | exuvia (female)

Family Lestidae (Spreadwings)

(none)

Male (vestigial genitalia)

Family Calopterygidae (Broad-winged Damselflies)

Family Coenagrionidae (Narrow-winged Damselflies)

(none)

Family Lestidae (Spreadwings)

(none)

Related Resources

Copyright © 2020 Walter Sanford. All rights reserved.

Sexing odonate exuviae (Anisoptera)

February 10, 2020

For some (but not all) species of odonate larvae/exuviae, sex is indicated by either a rudimentary ovipositor (female) or vestigial genitalia (male). These sex organs don’t look exactly the same for all species of dragonflies, but their function is identical.

The following photo gallery shows relatively clear examples that illustrate how to sex odonate exuvia in Suborder Anisoptera (Dragonflies).

Female (rudimentary ovipositor)

Family Aeshnidae (Darners)

10 DEC 2018 | Hairy Dragonfly (Brachytron pratense) | exuvia (female)

Family Cordulegastridae (Spiketails)

Family Corduliidae (Emeralds)

(none)

Family Gomphidae (Clubtails)

20 MAR 2018 | Brook Snaketail (Ophiogomphus aspersus) | exuvia (female)

Family Libellulidae (Skimmers)

(none)

Family Macromiidae (Cruisers)

(none)

Family Petaluridae (Petaltails)

Male (vestigial genitalia)

Male odonates have two sets of sex organs: primary genitalia located on abdominal segment nine (S9); and secondary genitalia located on abdominal segments two-to-three (S2-3).

Both sets of vestigial genitalia are clearly visible on the ventral side of some (but not all) specimens, such as the A. umbrosa exuvia shown below.

Family Aeshnidae (Darners)

Family Cordulegastridae (Spiketails)

(none)

Family Corduliidae (Emeralds)

Family Gomphidae (Clubtails)

26 MAR 2018 | Appalachian Snaketail (Ophiogomphus incurvatus) | exuvia (male)

Family Libellulidae (Skimmers)

Family Macromiidae (Cruisers)

Family Petaluridae (Petaltails)

(none)

Related Resources

Copyright © 2020 Walter Sanford. All rights reserved.

What is it?

February 7, 2020

It’s time for another exciting edition of “What is it?” Well, what is shown in the following photograph? If you think you know what it is, then please leave a comment. The answer will be provided in a post update.

03 FEB 2020 | Occoquan Regional Park | What is it?

Post Update

Congratulations to the two readers who correctly identified the mantis ootheca shown in the preceding photo! (See Comments/Responses, below.)

This is a Chinese Mantis (Tenodera sinensis) egg case, as indicated by the distinctive roundish shape of the ootheca. Chinese Mantis is a non-native species.

Copyright © 2020 Walter Sanford. All rights reserved.


%d bloggers like this: