Posts Tagged ‘exuvia’

Post update: Which family is it?

December 2, 2022

The following odonate exuvia is from a damselfly in Suborder Zygoptera.

The overall shape of the prementum (highlighted by a red rectangle) indicates this specimen is from Family Calopterygidae (Broad-winged Damselflies). Notice the embedded raindrop shape (highlighted by a purple rectangle), located toward the upper-center of the prementum — a key field mark for this family.

03 SEP 2022 | Powhatan County, VA USA | (exuviaventral side)

Two genera from Family Calopterygidae are common in the Commonwealth of Virginia: Hetaerina; and Calopteryx. For species in Genus Calopteryx the raindrop shape (Fig. 19) looks more like a diamond shape (Fig. 18), so it’s probably safe to infer this specimen is a species in Genus Hetaerina.

Related Resources

Post Update: Congratulations to Doug Mills, Wally Jones, and Bob Perkins for correctly identifying the family of this exuvia.

Doug and Wally looked at the shape of the prementum. Bob looked at the antennae.

The long middle segment on the antennae is the key, found only on Calopterygidae nymphs. Nymphs of the other families have antenna segments that are progressively shorter from base to tip. Source Credit: Bob Perkins.

Looking at the prementum should enable you to identify all three families; looking at antennae works for only one family.

Copyright © 2022 Walter Sanford. All rights reserved.

Which family is it?

November 29, 2022

An odonate exuvia was collected by Cindy Haddon Andrews on 03 September 2022 along the James River, near the Maidens Boat Landing in Powhatan County, Virginia USA. External gills (3) indicate this specimen is from a damselfly in Suborder Zygoptera.

Pattern recognition can be used to tentatively identify damselfly larvae/exuviae to the family level: the shape of the prementum is characteristic for each of the three families found in the mid-Atlantic region of the United States of America.

Your mission, should decide to accept it, is to identify the family to which the following damselfly exuvia belongs.

03 SEP 2022 | Powhatan County, VA USA | (exuviaventral side)

The camera lens was manually focused on the prementum, located near the anterior end of the exuvia.

Here is the same photo rotated 90° clockwise.

03 SEP 2022 | Powhatan County, VA USA | (exuviaventral side)

If you think you know the family, then please leave a comment. The correct answer will be revealed in a post update.

Related Resource: How to Identify Damselfly Exuviae to Family – a photo-illustrated identification guide by Walter Sanford.

Copyright © 2022 Walter Sanford. All rights reserved.

Archilestes grandis exuvia (female)

November 25, 2022

An odonate exuvia from a Great Spreadwing damselfly (Archilestes grandis) was collected by Edgar Spalding at a small private pond in Middleton, Wisconsin USA.

SEP 2022 | Middleton, WI | Archilestes grandis (exuvia, ventral side)

External gills (3), highlighted by a blue rectangle in the following annotated image, indicate the exuvia is from a damselfly in Suborder Zygoptera.

The camera lens was manually focused on the prementum, located near the anterior end of the exuvia (highlighted by a red rectangle). The overall shape of the prementum indicates this specimen is from Family Lestidae (Spreadwings); the unique shape of the palpal lobes (highlighted by a purple rectangle) indicates Genus Archilestes.

There are two species in Genus Archilestes in North AmericaArchilestes californicus; and Archilestes grandis. I think it’s reasonable to infer this individual is A. grandis since Wisconsin is far out of range for A. californicus.

SEP 2022 | Middleton, WI | Archilestes grandis (exuvia, ventral side)

This individual is a female, as indicated by the rudimentary ovipositor located on the ventral side of its abdomen, near the posterior end (highlighted by a green rectangle in the preceding annotated image).

Related Resources

Copyright © 2022 Walter Sanford. All rights reserved.

Iberian odonate larvae

September 16, 2022

During late-October 2021, I was contacted by Miguel A. Conesa-García, PhD, Profesor Tutor Biología, Diversidad Animal, Ciencias Ambientales, UNED-Málaga.

Miguel was working on finishing the second edition of his book about odonate larvae in the Iberian Peninsula (Spain and Portugal). When Miguel was almost finished, an adult male Wandering Glider dragonfly (Pantala flavescens) was spotted in Spain. P. flavescens is a new species of odonate for the region, so Miguel decided to add the new discovery to the species list in his book.

Cover photo, courtesy Amazon Books.

The following screen capture shows the search string I used to find the book on Amazon.

Screen capture, Amazon Books.

The book is richly illustrated with beautiful photos and diagrams. It’s abundantly evident I could learn a lot from the book — I wish there were an English Edition!

Miguel requested permission to use a photo of a Wandering Glider exuvia in my photoblog, published on 14 November 2018. I was, of course, willing to help.

Page excerpt from Miguel’s book, featuring my photo.

I’m mentioned in the acknowledgements at the end of the book. Regrettably my first name is misspelled and the Web address cited is no longer current. I took the liberty of annotating the page from Miguel’s book to provide the correct information.

Acknowledgements, p. 539 (annotated).

Acknowledgements, p. 539 (original).

Migratory Dragonflies

Wandering Glider is one of at least five major species of dragonflies known to be migratory in North America. P. flavescens is the only species of odonate known to occur on every continent except Antarctica.

The exuvia that I photographed is the “cast skin” from an odonate larva (nymph) that was collected in the field by Andy Davidson, a graduate student at Virginia Commonwealth University in Richmond, Virginia USA. Andy reared the larva in the laboratory as part of a research project entitled “Predator-Prey Interactions in a Changing World.”

Part of the value in rearing odonate larvae in the laboratory is knowing with certainty that an exuvia is from a particular species. This is perhaps the reason that Miguel chose to use my photo.

Related Resources

Copyright © 2022 Walter Sanford. All rights reserved.

Pantala versus Tramea exuviae/larvae

August 12, 2022

Sometime during the late 1950s or early 1960s, my father bought a new car. That was a big deal in our family. My family was poor, although I didn’t realize it when I was a young boy. We couldn’t afford a new car very often. I don’t remember many details about the car other than it was a sky blue Plymouth with tail fins. Big tail fins! My best guess is the car was a four-door Plymouth Fury, sold from 1957 – 1960.

Some odonate exuviae/larvae remind me of the tail fins on my father’s Plymouth automobile. Go figure. Anyway, pattern recognition can be used to make it a little easier to identify exuviae. For example, when I see an exuvia with long “tail fins,” my first thought is it’s probably from one of two genera, possibly three: genus Pantala; genus Tramea; or maybe genus Celithemis.

Dichotomous keys

The following couplet from Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, can be used to differentiate exuvia from Genus Pantala and Genus Tramea.

p. 37, Key to the Genera of the Family Libellulidae
12a – Superior abdominal appendage (epiproct) as long as, or longer than inferiors [paraprocts]. Pantala
12b – Superior abdominal appendage (epiproct) shorter than inferiors [paraprocts]. Tramea

Soltesz, p. 39.

Soltesz, p. 40.

Soltesz, p. 41.

Genus Pantala (Rainpool Gliders)

The genus Pantala includes two (2) species in North America: Spot-winged Glider (Pantala hymenaea); and Wandering Glider (Pantala flavescens).

Spot-winged Glider and Wandering Glider larvae/exuviae look similar. The lateral spines on abdominal segment nine (S9) are noticeably shorter for P. hymenaea (shown left) than P. flavescens (shown right) — a key field mark that can be used to differentiate the two species.

Genus Tramea (Saddlebags)

The genus Tramea includes seven (7) species in North America. Two of those species are found commonly in the Commonwealth of Virginia: Black Saddlebags (Tramea lacerata); and Carolina Saddlebags (Tramea carolina).

Carolina Saddlebags

A Carolina Saddlebags dragonfly (Tramea carolina) larva was collected by Andy Davidson near Richmond, Virginia USA, and reared to maturity. Andy saved the exuvia after emergence.

A vertical white line marks the mid-dorsal length of abdominal segment nine (S9), as shown in the following annotated image; the vertical black line labeled “mid-dorsal length” is the same length as the white line. Notice the lateral spines of abdominal segment nine (S9) are much longer than its mid-dorsal length.

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

One of the keys to identifying skimmer dragonflies to the species level is to carefully examine the anal pyramid (S10), including the cerci (sing. cercus), epiproct, and paraprocts. Notice the epiproct is shorter than the paraprocts.

There is a lot of “seaweed” (aquatic vegetation) clinging to the exuvia, especially noticeable at the posterior end. Some collectors like to clean their specimens; I prefer to photograph them “as is.”

Black Saddlebags

Athough adult Black Saddlebags dragonflies (Tramea lacerata) are relatively common in Virginia, the author has never seen an exuvia from this species.

Genus Celithemis (Pennants)

The genus Celithemis includes eight (8) species in North America. The author has a specimen from only one of these species in his collection.

Calico Pennant dragonfly (Celithemis elisa) evuvia was collected by Sue and John Gregoire at Kestrel Haven Migration Observatory. For more than a decade, Sue and John have closely monitored the annual emergence of a large population of C. elisa at their farm pond.

Notice the long lateral spines that look similar to larvae/exuviae in genus Pantala and genus Tramea.

Related Resources

Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz.

  • p. 36 = Key to the Genera of Family Libellulidae
  • p. 37 = Pantala, Tramea
  • p. 39 = Key to the species of genus Pantala: hymenaea; flavescens
  • p. 41 = Key to the species of genus Tramea: carolina; lacerta

A Checklist of North American Odonata – Including English Name, Etymology, Type Locality, and Distribution, by Dennis R. Paulson and Sidney W. Dunkle.

Copyright © 2022 Walter Sanford. All rights reserved.

Jumping spider

March 15, 2022

The following photo shows a tiny spider carcass (~3/16″ long) that was inside an exuvia (~1 3/4” long) from a Common Green Darner dragonfly (Anax junius). The exuvia was collected on 17 June 2021 from a small pond in Prince William County, Virginia USA. I discovered the spider long afterward — too late to save its life.

17 JUN 2021 | PNC. Wm. County, VA | Jumping spider

Thanks to Eva Weiderman and Joseph Girgente — members of the “Odonate Larvae and Exuviae” Facebook group — for their help in identifying the specimen as a jumping spider, Family Saticidae.

Salticidae is one of several families of spiders with eight (8) eyes. My take-away from reading the reference on BugGuide entitled “Spider Eye Arrangements” is identification of this specimen to the genus and species level is challenging at best and impossible at worst.

In contrast, it’s well known that spiders use odonate exuviae for shelter. I wish the jumping spider had come out of its most excellent hidey-hole sooner!

17 JUN 2021 | PNC. Wm. County, VA | Anax junius exuvia

Related Resources

Tech Tips

The tiny jumping spider was photographed using a Panasonic Lumix FZ-300, Raynox DCR-250 close-up filter, Godox X2To/p flash trigger, and Godox TT685F plus Altura flash modifier. Camera settings: ISO 100 | f/7.1 | 1/60 s | 56.9mm (316mm, 35mm equivalent).

Raynox DCR-250 close-up filter” is a blog post in which I provide more information about how I use the Raynox with my Panasonic Lumix superzoom bridge cameras.

Copyright © 2022 Walter Sanford. All rights reserved.

Collecting odonate exuviae

January 7, 2022

Odonates (dragonflies and damselflies) are aquatic insects that spend most of their life as larvae (nymphs) that live in water; this stage of their life cycle can last from a few months to a few years. Finally, they emerge from the water and metamorphose into adults in order to reproduce; their offspring return to the water and the cycle begins again.

I think it’s safe to say less is known about odonates during the aquatic phase of their lives than during the terrestrial phase. In my opinion, there is a real opportunity to make a significant contribution to the body of scientific knowledge about odonates by collecting and identifying exuviae.

What can be learned from collecting odonate exuviae?

Here are two examples that illustrate why I think it’s important to collect and identify odonate exuviae.

I’ve never seen an adult Arrow Clubtail dragonfly (Stylurus spiniceps). That’s not surprising, since many experienced odonate hunters classify them as uncommon to rare.

But I know a place along the Potomac River in Fairfax County, Virginia USA where I am certain Arrow Clubtail dragonflies live. How do I know? Because I collected a Stylurus spiniceps exuvia from that location on 04 August 2016.

An Arrow Clubtail dragonfly (Stylurus spiniceps) exuvia collected at Riverbend Park, Fairfax County, Virginia USA.

04 AUG 2016 | Fairfax County, VA | Stylurus spiniceps exuvia (ventral)

More recently, my good friend and odonate hunting buddy Mike Boatwright discovered a small breeding population of Zebra Clubtail dragonflies (Stylurus scudderi) at an undisclosed location in Amherst County, Virginia USA. For several years, Mike found 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.

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

Do you need a permit in order to collect odonate exuviae?

A strict interpretation of the Code of Virginia might lead one to think a permit is required.

It is unlawful to collect animal parts, such as feathers, claws, and bones without a permit (4 VAC 15-30-10 and §§ 29.1-521 and 29.1-553). Source Credit: Overview: Collecting, Exhibiting, and Releasing Wildlife, Virginia Department of Wildlife Resources.

That being said, it appears there is an exception for Phylum Arthropoda.

At this time no DWR permit is required for the following: Phylum Arthropoda EXCEPT for the Superfamilies Astacoidea & Parastacoidea (Crayfish) – Arthropoda includes: Insects, arachnids, millipedes, centipedes and other crustaceans (EXCEPT Crayfish) such as: isopods, amphipods etc. … Source Credit: Overview: Collecting, Exhibiting, and Releasing Wildlife, Virginia Department of Wildlife Resources.

I interpret the Code of Virginia to mean a permit IS NOT required to collect odonate exuviae.

How to collect odonate exuviae

Before you collect an exuvia, please photograph the specimen in situ. Record the date, location, and species (if known). A photograph is especially valuable when both the adult and exuvia are shown in the same photograph.

17 JUN 2021 | PNC. Wm. County | Anax junius exuvia (lateral)

Here are my tips for collecting exuviae. Bear in mind, I’m a perfectionist. It’s a fault, but hey, I am what I am and that’s all that I am.

I carry several items in my camera bag: a small plastic spoon; narrow strips of heavy card stock (maybe 3/8″ wide and two inches long); a small pair of scissors (one of three tools in a simple Swiss Army knife); and small plastic containers.

“Go kit” for collecting odonate exuviae.

I’m guessing most people just grab an exuvia with their fingers, but whenever I do that I hear a crunching sound that makes me cringe and parts tend to break off, e.g., legs.

If the exuvia is on a sandy stream bank, then I scoop the specimen with a spoon. If the specimen is clinging to something like a rock or wooden dock, then I slide the handle of the spoon under the body and gently pry it off the surface. Those little grabbers on the end of their legs are very “grippy,” so “gently” is the operative word. If the handle of the spoon won’t fit under the body, that’s when I use the card stock.

If the exuvia is clinging to vegetation, e.g., a cattail, then make the “peace sign” with one hand and insert the stem up to the notch between your pointer- and middle fingers and then close those fingers. Put your hand BELOW the exuvia, palm up, like a cup (in case the specimen falls off the stem). Use scissors to cut the stem below your fingers/hand and a little above the exuvia. Put the specimen in a collecting container, including the stem.

I use large plastic pill bottles. (I take eye vitamins that come in a wide-mouth bottle, perfect for big specimens with long legs such as cruisers and Dragonhunter.) I also use the smallish plastic containers for Philadelphia cream cheese — they can be “nested,” allowing you to carry several containers without taking up much space.

There, now you know more about how to collect odonate exuviae than you ever wanted to know!

What are the take-aways?

Hey, I get it — building a collection of odonate exuviae and learning to identify them might not interest you. But I can assure you there are many people like me who are interested in odonate exuviae who would love to have specimens that you find and collect.

I’m not necessarily saying you should go out hunting specifically for exuviae, but I am saying when you go hunting adult dragonflies and damselflies please be on the lookout for exuviae and collect them when you find them (and I predict you will).

In this way, there is a multiplier effect that will result in the collection of more specimens than a single individual is likely to find. In turn, this should help to advance our understanding of the odonates of Virginia.

Copyright © 2022 Walter Sanford. All rights reserved.

Determining final instar the Cham way

December 14, 2021

Did you notice I added a new text label to the annotated image of an exuvia from a Comet Darner dragonfly (Anax longipes) featured in my last two blog posts? I added the label in order to make the connection between this image and related ideas discussed in two other relatively recent blog posts (See Related Resources, below).

Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back. “S4” stands for abdominal segment four.

Counting odonate abdominal segments can be challenging sometimes. A good strategy to avoid mis-numbering is to begin counting abdominal segments from S10 (located toward the posterior end of larvae (nymphs)/exuviae) and work toward the thorax.

Final instar, the Cham way

There is a simpler way to estimate final instar than calculating instar equivalent.

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 at the preceding annotated image. Notice the tips of the wing pads reach the fourth abdominal segment (S4), indicating the dragonfly larva that emerged from this exuvia had reached final instar. And that leads to the other idea I mentioned at the outset of this blog post.

Every odonate exuvia is a cast skin of the larva at F-0, the final instar, before it emerges to become an adult.

Turns out that’s another nugget of gold paraphrased from Steve Cham’s beautiful little book.

Post Update

The beauty of the Cham way of determining final instar is it’s simplicity. That’s the upside. The downside is there’s no way to determine the actual instar when it isn’t F-0.

For example, the following composite image shows dorsal views of a Common Green Darner (Anax junius) nymph (larva) and exuvia. As expected, the exuvia is F-0 because its wing pads cover S4. On the other hand, the nymph is F-? because its wing pads only reach S2.

Image used with written permission from Freda van den Broek.

Photo Credit: Both specimens (shown above) were collected by Freda van den Broek. The nymph was collected on 06 April 2020 from the Milwaukee River in Ozaukee County, Wisconsin USA, photographed, and released unharmed. The exuvia was collected from Ozaukee County too.

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Proof of concept, revisited

December 10, 2021

In this blog post I’m going to show you how I used Photopea to annotate one of my photos. The workflow using Photopea is virtually identical to the way I annotate photos using Adobe Photoshop.

The original photo was edited using Apple Aperture (a discontinued photo editor) and Photoshop (for spot removal and sharpening). I could have attempted to edit the photo using Photopea but that wasn’t the point of my “Proof of concept” blog post.

Finished project

The first screen capture shows the finished project — I used it to reverse-engineer the steps that I took to create the annotated image and the settings I made along the way.

The “Layers” panel (located in the right sidebar) shows the finished project is compromised of seven layers, listed from bottom to top in the order they were created.

The “Background” layer is the photo itself. Go to File / Open… and navigate your computer to find a photo you would like to annotate.

View / Rulers

Before proceeding, it’s helpful to turn on “Rulers.” More about that later. In the Photopea menu bar, go to View and check Rulers.

Tech Tips: command-R (macOS) is a keyboard shortcut that can be used to toggle Rulers on/off.

The “View” menu also includes “Zoom In” and “Zoom Out” plus the associated keyboard shortcuts.

Press and hold the spacebar. Notice the arrow-shaped cursor turns into a hand that can be used to drag the canvas around the work space.

Post Update: View / Screen Mode > Fullscreen will scale up the Photopea window to fit the size of your computer screen. Fullscreen mode makes it much easier to work on fine details, especially when used in combination with the “Zoom Tool” and “Hand Tool”; the icon for both tools appears in the lower part of the left sidebar. Try it — you’ll like it! Uncheck “Fullscreen” in order to return to the desktop view. By the way, did you notice I added another guide line and Text layer for a follow-up blog post?

Text Tool settings: Title

The title is the first layer I added using the following selections: IBM Plex Sans (font type); SemiBold (font style); Size = 150 px; Color = Black; and “Aa” = Sharp.

Tech Tips: Text size is measured in pixels, not points. I’m not sure Photopea is calibrated correctly to convert points to pixels. Test it yourself using one of many online points-to-pixels calculators such as PT to PX Converter.

No matter, click the down arrow beside text “Size” and simply use the slider to select a text size that you like. You can also highlight the pixel size and type the exact number you prefer.

To begin adding text to your project, select the “Text Tool” (located in the left sidebar), click an insertion point on the photo and start typing. The default name for the new layer is “Text layer 1, 2, 3, etc.”

When you are finished, either delete the layer by clicking the “Cancel” button (X icon located near the right end of the Photopea menu bar) or save changes made to the layer by clicking the “Confirm” button (checkmark icon located to the right of the X) and the layer name changes so it is the same as the text you typed. In this case, I shortened the name of the layer to “Comet Darner dragonfly.”

With the layer selected, click on the “Move Tool” (left sidebar, at the top) and click-and-drag the text to reposition it exactly where you like.

Text Tool settings: Labels

Next I added a layer for “eye (1 of 2),” one of several labels for parts of the anatomy, using the following selections: IBM Plex Sans (font type); Regular (font style); Size = 100 px; Color = Black; and “Aa” = Sharp.

Tech Tips: The “Sharp” setting is used to avoid text with “jaggies,” that is text with saw tooth edges.

As an aid for aligning text, I created a blue guide line by clicking on the ruler along the top of the screen and dragging down to position the guide line on the photo. The guide line can be repositioned using the “Move Tool.”

Line Tool settings

The next layer I added is an arrow that points from the label to the anatomical part, in this case an eye. The settings I used for “Arrow 1” are shown in the following screen capture.

Tech Tips: Add a new vertical guide line for Arrow 1 by clicking on the ruler along the left side of the screen and dragging to the right to position the guide line on the photo. Right-click on the “Rectangle Tool” and select the “Line Tool.” I used shift-click-and-drag to draw a straight arrow that is aligned with the new blue guide line.

Add more layers

I followed the same steps described above to add a Text layer for “wing pads,” a new guide line for Arrow 2 and an arrow that points from the label to the anatomical part, and another Text layer for “prementum.”

Saving / Exporting

I saved the final image as a Photoshop document by selecting File / Save as PSD. The resulting PSD file can be reopened in Photopea in order to continue working on the project. Post Update: .psd files created by Photopea can be opened in Adobe Photoshop, although it is likely the font(s) you chose to use in Photopea are not available in Photoshop. Photoshop will prompt the user to resolve the problem.

I also saved the file as a PNG by selecting File / Export as.

What are the take-aways?

Open Photopea in a Web browser: (For what it’s worth, I prefer “Google Chrome.”) Since Photopea is Web-based, it runs on desktop computers, laptop computers, tablets, and smart phones. Having said that, I think it would be challenging to annotate a photo with a tablet or phone unless those devices are used in combination with an external keyboard and mouse. Not impossible, but definitely challenging.

My dear friend Phil Wherry passed away too long ago. Phil was my tech guru for many years. I’m the type of person who suffers from “approach avoidance” — I like to know what will happen BEFORE I do something. One of the best bits of tech advice Phil shared with me is “Don’t be afraid to experiment and see what happens.” That’s exactly what I did when I used Photopea to annotate one of my photos and I encourage you to do likewise. Good luck!

Related Resources

Copyright © 2021 Walter Sanford. All rights reserved.

Proof of concept

December 7, 2021

Can Photopea be used to annotate photographs? Yes!

Do the results look as good as photos of the same subject that were annotated using Adobe Photoshop? You be the judge.

Comet Darner (Anax longipes) | exuvia (lateral)

In my opinion the results are of comparable quality and that’s saying a lot considering this is my first attempt at using Photopea to annotate a photo.

As expected, the workflow flowed slowly since this was the first time I used many of the tools featured in Photopea.

I saved the final image as a Photoshop document by selecting File / Save as PSD. The resulting PSD file can be reopened in Photopea in order to continue working on the project. I also saved the file as a PNG by selecting File / Export as.

The Backstory

The preceding photo shows an exuvia from a Comet Darner dragonfly (Anax longipes) that was collected by Stanley Caveney on 19 July 2021 from a pond at MeadowWoods in West Elgin, Ontario, Canada. Sincere thanks to Stan for kindly sharing this beautiful specimen!

Related Resource: Learn Photopea

Copyright © 2021 Walter Sanford. All rights reserved.

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