Archive for the ‘How To’ Category

Epitheca cynosura exuvia

April 26, 2017

On 13 April 2017, a late-stage emergent teneral female Common Baskettail dragonfly (Epitheca cynosura) was observed at Painted Turtle Pond during a photowalk around Occoquan Bay National Wildlife Refuge, Prince William County, Virginia USA.

Several dragonfly exuviae were collected near the same location as the emergent teneral female. All of the exuviae look identical, although there is some variation in size. A two-step process was used to verify the genus and species for one of the larger exuvia.

  • Determine the family.
  • Determine the genus and species.

This specimen is approximately 22 mm (~0.87 in) in length.

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 that covers the face, characteristic of four families: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • There is no horn on top of 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 [See Photo No. 7.]: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts. [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).

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

Notice that dorsal hooks are present and well developed on most abdominal segments.

No. 4 | Common Baskettail (Epitheca cynosura) | exuvia (dorso-lateral)

A lateral view of the exuvia provides a good look at the labium, also known as the mentum, a two-segment hinged “jaw” that is used to grab food: the prementum is the segment of the labium closer to the mouth; the postmentum is the segment closer to the base of the head.

The white filaments that extend from the split in the thorax (as shown in Photo No. 1-7) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

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

A closer view of the head shows two “bumps” that may be a pair of tubercles.

Step 2. Genus and species

Characters from Identification Keys to Northeastern Anisoptera Larvae, dichotomous keys compiled by Ken Soltesz, were used to identify the genus and species for the exuvia. Although palpal/mental setae were not examined, all other characters match Epitheca cynosura.

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

Alternate Key to the Genera of the Family Corduliidae, p. 29.

Key to the species of the genus (subgenus) Tetragoneuria, p. 32.

No. 7 | Common Baskettail (Epitheca cynosura) | exuvia (anal pyramid)

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

The last photo shows a ventral view of the exuvia. The vestigial hamuli located between abdominal segments two and three (S2-3) strongly suggests this individual is a male, therefore this specimen probably is not the same exuvia from which the teneral female emerged.

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

Tech Tips:

The following equipment was used to shoot all of the preceding photographs: Canon EOS 5D Mark II digital camera, in manual mode; Canon EF100mm f/2.8L Macro lens (set for manual focus) plus a Kenko 20mm macro automatic extension tube; Canon 580EX II external flash tethered to the camera by a coiled six-foot Vello Off-Camera TTL Flash Cord for Canon Cameras, off-camera, in manual mode; the Canon flash optically triggered a small Nissin i40 external flash (in SF mode) used for backlight; and a Sunpak LED-160 Video Light with a white translucent plastic filter used for side light.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources:

Editor’s Note: Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for verifying my tentative identification, and for sharing some good odonate nymph knowledge regarding vestigial hamuli!

Copyright © 2017 Walter Sanford. All rights reserved.

More focus stacking with CamRanger

April 10, 2017

When I started experimenting with completely automated focus stacking using CamRanger, I couldn’t tell what, if anything, was happening. In fact, I wasn’t sure the process was working as advertised. So I devised a plan to photograph a simple subject (a six-inch ruler in this case) and use “focus peaking” to track what happened. By the way, it’s worth noting that my Canon EOS 5D Mark II DSLR camera doesn’t feature focus peaking, but the CamRanger app does!

During initial testing, I shot several small focus stacks. The following screen capture shows the display on my iPad mini (with retina display) running the CamRanger app; the focal plane of the lens is highlighted by red focus peaking.

Here’s a screen capture from another test, showing the final location of the focal plane (highlighted in red).

I made a movie that demonstrates what happens when CamRanger creates a focus stack. It was fun to watch the focal plane advance along the ruler as CamRanger captured the shots automatically!

The movie begins with a small focus stack using a “Large” step size (the largest increment of three options). When focus stacking is active, notice that most of the screen is covered by a translucent gray layer that prevents the user from changing settings accidentally. I cancelled the focus stack after two shots. Next I changed the step size to “Medium” and started a new stack. Notice that the focal plane of the lens begins where the last focus stack ended. The new step size is noticeably smaller.

Automated focus stacking using CamRanger (2:12)

As shown in the right side bar of the CamRanger app, I set the camera to shoot RAW plus small JPG. Both file types are recorded on the memory card in the camera; thumbnail versions of the JPG files are displayed at the top of the iPad screen. Although I usually shoot RAW only, JPG files can be transferred via WiFi faster than RAW files!

I set the CamRanger app to wait 10 seconds between shots, in order to allow adequate time for the camera to write the image files to the memory card, transfer the JPG thumbnail from the camera to the app, rack the lens to the next focal plane, and for the external flash units to power cycle.

My first finished automated focus stacks

I created a 30-layer focus stack using a medium increment. The following photo shows the JPG version of the first layer.

I used Adobe Photoshop CC 2017 to create a medium-increment focus stack using the small JPGs because they can be processed faster than RAW. The resulting composite image is shown below.

Finally, here’s the resulting composite image of a five-layer focus stack created from large increment/medium JPG photos. In my opinion, the output looks almost as good as the composite image created from five times as many layers.

Lessons Learned

  • Given a choice, run the CamRanger app on the most powerful tablet you own. I use my iPad mini rather than iPad 3 (with retina display). Although the iPad 3 screen is larger than the iPad mini, it features a slower processor. That being said, the iPad 3 is perfectly suitable for using the CamRanger app for other less processor-intensive tasks.
  • Some lenses, such as my Canon EF100mm macro lens, can be set for manual focus and the CamRanger app can still rack focus automatically. It may be necessary to set other lenses for automatic focus in order to work with focus stacking in CamRanger.
  • If possible, use continuous light sources rather than external flash units. I love me some flash triggers, but they’re not 100% reliable. If you’re shooting stills and the flash fails to fire, it’s no big deal — just shoot another shot. Not so when you miss a critical focus layer. I use a combination of two small LED light sources and a Canon Speedlite tethered to the camera by a Vello flash cable; the Canon flash optically triggers a small Nissin i40 external flash (in SD mode) used for backlight.
  • Turn off “sleep mode’ for my Canon 580EX II Speedlite. (C.Fn-01 set for Disabled.)
  • It’s challenging to determine how many layers to shoot for a given focus stack, especially when using smaller step sizes. Don’t sweat it! Simply shoot more layers by starting where the focal plane is at the end of the last focus stack. Repeat as necessary until you capture as many layers as needed.

What’s next?

Going forward, my plan is to experiment with automated focus stacking using subjects that are more complex than the ruler featured in this post. Preliminary testing suggests it could be challenging to create perfect composite images of objects that are more three-dimensional than the ruler.

Sidebar

I used QuickTime to create the embedded movie (shown above) by tethering my iPad mini to a MacBook Air laptop computer and following the excellent directions provided in How To Display your iPad or iPhone on your Mac (9:44), a tutorial video by Terry White, Adobe Evangelist.

Related Resources

Full disclosure: There are hardware/software solutions for wireless tethering and automated focus stacking that are less expensive than CamRanger. Remember, you get what you pay for!

Copyright © 2017 Walter Sanford. All rights reserved.

Another foray into focus stacking

April 2, 2017

I used CamRanger to remotely control my Canon 5D Mark II DSLR camera with an Apple iPad 3 (with retina display). The camera was set for manual exposure and One-Shot AF. I used an aperture of f/5.6 with my Canon 100mm macro lens; I think I’ll use f/8 next time.

Apple iPad 3 (with retina display) | screenshot of CamRanger app

The CamRanger app for Apple iOS can be used to set the focus point by tapping on the iPad screen. I focused on the toy dragonfly in approximately 10 places and tapped the “Capture” button to take a photo. The following photo shows one of the resulting images, focused on the head of the dragonfly.

ISO 100 | f/5.6 | 1/200s | Manual White Balance (Flash use)

Adobe Photoshop CC 2017 was used to create a “focus stack” composite image. As you can see, most of the toy dragonfly is in focus but there are some places that are slightly blurry/ghostly. The obvious solution: Focus on more places (that is, take more pictures), although that might be unnecessary using an aperture of f/8 or smaller.

Composite image created using Adobe Photoshop CC 2017.

Going forward, my plan is to progress from manually setting the focus point by tapping on the iPad screen to using the automated focus stacking feature in the CamRanger app. Baby steps, Bob!

Tech Tips:

The following equipment was used to shoot all of the photographs in the focus stack: Canon EOS 5D Mark II digital camera, in manual mode; Canon EF100mm f/2.8L Macro lens (set for automatic focus); Canon 580EX II external flash, off-camera, in manual mode; Canon 580EX external flash, off-camera, in manual mode; and a Yongnuo YN-622C-TX E-TTL II Wireless Flash Controller for Canon plus a two-pack of Yongnuo YN-622C II E-TTL Wireless Flash Transceivers for Canon. Additional backlight was added to the scene using a Nissin i40 external flash unit (off-camera, in SF mode).

Adobe Photoshop CC 2017 was used to create the focus stack and post-process the composite image.

Copyright © 2017 Walter Sanford. All rights reserved.

Macromia illinoiensis exuvia

March 15, 2017

Post update: Macromiidae exuvia

When this blog post was published on 19 April 2016, I was a novice at identifying odonate exuviae and I was just starting to get serious about studio macro photography. At the time, I was satisfied to be able to identify the dragonfly exuvia as a member of the Family Macromiidae (Cruisers).

What’s new?

I’ve learned a lot since then, including the identity of the specimen to the genus/species level. This is a Swift River Cruiser dragonfly (Macromia illinoiensis) exuvia that was collected along the Potomac River in Fairfax County, Virginia USA.

The first annotated image shows several characters that were used to identify the exuvia to the family level, including a mask-like labium featuring spork-like crenulations and a horn between its pointy eyes.

Swift River Cruiser (Macromia illinoiensis) | exuvia (face-head)

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

The following dorsal view of the exuvia provides enough clues to identify the specimen to the genus/species level.

Swift River Cruiser (Macromia illinoiensis) | exuvia (dorsal)

The lateral spines of abdominal segment nine (S9) do not reach the tips of the inferior appendages (paraprocts), and if you look closely at the full-size version of the preceding photo then you should see a small mid-dorsal hook on abdominal segment 10 (S10). These characters indicate the genus is Macromia.

Notice the lateral spines of abdominal segments eight and nine (S8-9) are “directed straight to rearward,” indicating the species is illinoiensis.

Where it all began.

The last photo shows a teneral male Swift River Cruiser dragonfly clinging to the exuvia from which it emerged — the same exuvia featured in this post! Matt Ryan collected the exuvia after the adult dragonfly flew away from its perch. When Matt gave the exuvia to me several years later, he was unable to remember where it was collected. As soon as I was able to identify the exuvia to the genus/species level, I remembered seeing the following photo posted in one of Matt’s spottings on Project Noah.

Photo used with permission from Matthew J. Ryan.

With a little detective work, I was able to solve the mystery of the specific identity of the exuvia as well as when and where it was collected. Like I said, I’ve learned a lot since I published the first blog post related to this specimen!

Related Resources:

Editor’s Notes: A funny thing happened on the way to the forum. I rediscovered the “Key to the Genera of the Family Macromiidae” (p. 27, shown above) while paging through the document Identification Keys to Northeastern Anisoptera Larvae in search of the “Key to the Genera of the Family Corduliidae” (page 28). One look at the line drawing at the bottom of p. 27 and I knew the specific identity of the cruiser exuvia.

I need to refresh this blog post with more annotated images of the Macromia illinoiensis exuvia, including one that clearly shows the mid-dorsal hook on S10, but I was so eager to update the old post that I couldn’t wait to shoot and post-process the new images.

Copyright © 2017 Walter Sanford. All rights reserved.

How to Identify Damselfly Exuviae to Family

March 11, 2017

There are five families of damselflies (Suborder Zygoptera) in the United States of America, although only three families occur in the mid-Atlantic region: Family Calopterygidae (Broad-winged Damselflies)Family Coenagrionidae (Narrow-winged Damselflies); and Family Lestidae (Spreadwings).

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; mnemonics can be used to remember each distinctive shape.

Family Calopterygidae (Broad-winged Damselflies)

Family Calopterygidae features a prementum with a shape that looks somewhat similar to Family Coenagrionidae. Look for an embedded raindrop shape, located toward the upper-center of the prementum.

An Ebony Jewelwing damselfly (Calopteryx maculata) exuvia was collected along a small stream located in eastern Fairfax County, Virginia USA.

Family Calopterygidae (Broad-winged Damselflies) | prementum

Family Coenagrionidae (Narrow-winged Damselflies)

The shape of the prementum for Family Coenagrionidae reminds me of a keystone.

A Narrow-winged Damselfly exuvia — probably Argia sp. (it’s a work in progress) — was collected along the Potomac River in Fairfax County, Virginia USA. This individual is a female, as indicated by the rudimentary ovipositor located on the ventral side of her abdomen.

Family Coenagrionidae (Narrow-winged Damselflies) | ventral

The lamellae, also known as caudal lamellae, are external structures used by damselfly larvae for both respiration and locomotion. In contrast, the respiratory system for dragonfly larvae is internal. Characteristics of the caudal lamellae (including shape of/patterns on) are some of the clues that can be used to identify damselflies to the genus/species level.

Family Lestidae (Spreadwings)

The unique shape of the prementum for Family Lestidae reminds me of a rattle (musical instrument).

A damselfly exuvia from the Family Lestidae (Spreadwings) was collected from a small vernal pool located in eastern Fairfax County, Virginia USA. Although the genus/species is unknown (again, it’s a work in progress), both Slender Spreadwing (Lestes rectangularis) adults and Southern Spreadwing (Lestes australis) adults were observed at the vernal pool on the same day this specimen was collected.

Family Lestidae (Spreadwings) | prementum

Related Resources: The first step is the hardest, as the saying goes. In this case, it’s easier to identify damselfly larvae/exuviae to the family level than it is to identify specimens to the genus/species level. There are relatively few resources, especially online resources. The following links to two dichotomous keys and a pattern-matching guide for caudal lamellae should help you get started. Many of the same species of damselflies that are known to occur in Michigan, Florida, and the Carolinas can be found in the mid-Atlantic region.

Copyright © 2017 Walter Sanford. All rights reserved.

More power!

February 19, 2017

Like Tim “The Tool Man” Taylor, I like more power. (Grunt, grunt.) Actually, I need more power for some of the macro photography that I do, especially when I’m shooting small specimens such as odonate exuviae.

For the past few months, I’ve experimented with several ways to get more “oomph” from my Canon EF100mm f/2.8L Macro lens. I’ve tested three types of photo gear used in combination with the macro lens including extension tubes, a close-up filter, and a tele-extender.

The first photograph shows the following equipment, from left-to-right: Canon EOS 5D Mark II digital camera; Canon Extender EF 1.4x II (white); Kenko 20mm macro automatic extension tube; Canon EF100mm f/2.8L Macro lens; 67-52mm step-down ring; 52-42mm step-down ring; Raynox DCR-250 close-up filter (covered by lens cap).

Canon EOS 5D Mark II macro photography kit.

Canon EOS 5D Mark II macro photography kit.

For most macro subjects, my “base kit” includes the 100mm macro lens plus a 20mm extension tube. Adding one or more extension tubes reduces the minimum focusing distance of the lens. Adding a close-up filter enables me to zoom in closer to the subject. The tele-extender effectively changes the focal length of the macro lens from 100mm to 140mm, resulting in a 1 f/stop loss of light. Some photographers contend that adding a tele-extender can result in a loss of sharpness. Your results may vary from mine, but I find the increased magnification that results from using a tele-extender is worth a small loss of sharpness.

The Canon Extender EF 1.4x II is incompatible with the Canon EF100mm f/2.8L Macro lens — it is impossible to connect the two devices directly. It’s worth noting that incompatible doesn’t mean they don’t work together — they do, as long as an extension tube is added in-line between the tele-extender and lens.

The last photograph shows the following equipment, couterclockwise from the upper-left: “snap-on universal adapter” for Raynox DCR-250 close-up filter; Raynox close-up filter mounted on a 52-43mm step-down ring; and a 67-52mm step-down ring.

Several mounting adapters for Raynox DCR-250 close-up filter.

Several mounting adapters for Raynox DCR-250 close-up filter.

The Raynox DCR-250 close-up filter comes with a “snap-on universal adapter” for mounting the filter on lenses with a filter size from 52-67mm. The adapter clips on the front of a lens the same as a lens cap. In my opinion, that’s OK for use in a home photo studio but less than ideal for use in the field.

I bought two inexpensive step-down rings that can be used to mount the close-up filter more securely: a 52-43mm step-down ring enables me to mount the Raynox DCR-250 on either the “Nifty 50” (a 50mm lens for my Canon DSLR) or Panasonic DMC-FZ150 superzoom bridge camera, my go-to kit for photowalking; a 67-52mm step-down ring enables me to connect the 52-43mm/Raynox close-up filter combo (shown above) with my Canon 100mm macro lens.

In case you’re wondering whether vignetting is a problem when using two step-down rings with the Canon 100mm macro lens, it isn’t. As it turns out, the front lens element is recessed quite a bit from the lens barrel so the step-down rings cover little if any glass.

Related Resources:

Afterthoughts

Two thoughts occurred to me after this post was published.

  1. As a result of limited testing, I concluded that it is possible to stack two or three extension tubes in order to achieve the same result as using a tele-extender without any loss of sharpness. Problem is, the minimum focusing distance is so small that the working distance between the lens and subject is too close for comfort. Adding the tele-converter provides more magnification at a slightly longer working distance.
  2. Caution: Connect the 52-43mm step-down ring to the 67-52mm step-down ring BEFORE connecting the combo to the 100mm macro lens. Otherwise there is some risk of scratching the front element of the macro lens.

Copyright © 2017 Walter Sanford. All rights reserved.

Stylurus spiniceps exuvia

January 6, 2017

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. In a nutshell, this is one of many reasons I’m learning to identify odonate exuviae.

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

No. 1 | Arrow Clubtail (Stylurus spiniceps) | exuvia (face-head)

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

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 I used to identify the exuvia as a member of the Family Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in photo No. 2 and 3.
  • Antennae are club-like (not thin and thread-like, as in Aeshnidae).
  • Eyes not exceptionally large compared to the size of the head (not large, as in Aeshnidae).
An Arrow Clubtail dragonfly (Stylurus spiniceps) exuvia collected at Riverbend Park, Fairfax County, Virginia USA.

No. 2 | Arrow Clubtail (Stylurus spiniceps) | exuvia (face-head)

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

Genus and species

Gomphidae is the second largest family of dragonflies, so it can be challenging to identify some specimens to the genus and species level. As it turns out, Arrow Clubtail exuviae are easy to identify because their abdominal segment nine (S9) is unique among Gomphidae: S9 is more than twice as long as it is wide at its base, as shown in the following annotated image.

The length of the exuvia is approximately 4.2 cm (~1.7 in).

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

No. 3 | Arrow Clubtail (Stylurus spiniceps) | exuvia (ventral)

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

More photos of the exuvia are shown below.

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

No. 4 | Arrow Clubtail (Stylurus spiniceps) | exuvia (dorsal)

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

No. 5 | Arrow Clubtail (Stylurus spiniceps) | exuvia (dorso-lateral)

Tech Tips:

The following equipment was used to shoot all of the preceding photographs: Canon EOS 5D Mark II digital camera, in manual mode; Canon EF100mm f/2.8L Macro lens (set for manual focus) plus a Kenko 20mm macro automatic extension tube; Canon 580EX II external flash, off-camera, in manual mode (Master); Canon 580EX external flash, off-camera, in manual mode (Slave); and a coiled six-foot Vello Off-Camera TTL Flash Cord for Canon Cameras. A Raynox DCR-250 close-up filter was used for Photo No. 2.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources:

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

In long form, the decision tree is as follows (assuming the convention of labeling the two branches of each dichotomy as “a” and “b”, e.g. 1a, 1b, etc.):

p. 17, Key to the species of the genus Stylurus
1a – Abdominal segment 9 twice as long as wide at base. (spiniceps)

Editor’s Note: This is the 1,000th post on my photoblog. That’s a major milestone, and quite candidly, one I never expected to reach. Who knew I have so much to show-and-tell?

Copyright © 2017 Walter Sanford. All rights reserved.

Tramea carolina exuvia

December 12, 2016

An exuvia from an unknown species of dragonfly was collected on 04 October 2016 at Mason Neck West Park (MNWP), Fairfax County, Virginia USA. A two-step process was used to identify the genus and species of the specimen.

Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video, Identifying dragonfly larva to family (8:06).

The exuviae has a mask-like labium (not flat) with evenly-toothed crenulations, indicating this individual is a member of Family Libellulidae (Skimmers). [See Photo No. 2.]

Genus and species

A dichotomous key was used to tentatively identify the exuvia as Carolina Saddlebags dragonfly (Tramea carolina), as indicated by the following morphological characteristics.

  • No dorsal hooks on any abdominal segments.
  • Lateral spines of abdominal segment nine (S9) are much longer than its mid-dorsal length. Lateral spines on segment eight (S8) are nearly as long as on segment nine (S9).[See Photo No. 3.]
  • Superior abdominal appendage (epiproct) is shorter than inferior abdominal appendages (paraprocts). [See Photo No. 3.]

Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for verifying my preliminary observations and tentative identification!

No. 1

The specimen is approximately 2.4 cm (~0.9″) in length. Notice there are no dorsal hooks on any abdominal segments.

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

No. 1 | Carolina Saddlebags (Tramea carolina) | exuvia (dorso-lateral)

The white filaments that extend from the split in the thorax (as shown in Photo No. 1-2, 4-6) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

No. 2

The eyes are rounded and widely separated. Notice the mask-like labium (sometimes referred to as “spoon-shaped”) with evenly-toothed crenulations along the margins between two lateral lobes.

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

No. 2 | Carolina Saddlebags (Tramea carolina) | exuvia (face-head)

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

No. 3

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.

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

No. 3 | Carolina Saddlebags (Tramea carolina) | exuvia (anal pyramid)

(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.”

More photos of the exuvia are shown below.

No. 4

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

No. 4 | Carolina Saddlebags (Tramea carolina) | exuvia (dorsal)

No. 5

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

No. 5 | Carolina Saddlebags (Tramea carolina) | exuvia (face-head)

No. 6

A dragonfly exuvia (Tramea carolina) collected at Mason Neck West Park, Fairfax County, Virginia USA.

No. 6 | Carolina Saddlebags (Tramea carolina) | exuvia (anal pyramid)

Tech Tips:

The following equipment was used to shoot the preceding photographs:

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources:

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

Assuming the convention of labeling the two branches of each dichotomy as “a” and “b”, e.g. 1a, 1b, etc., a list of branches in the decision tree that I used to identify the genus of the dragonfly exuviae is as follows: 1b; 4b; 5b; 10a; 11b; 12b Tramea. A supplemental key featuring one dichotomy was used to identify the species: 1a carolina BINGO!

In long form, the decision tree is as follows:

p. 36, Key to the Genera of the Family Libellulidae
1b – Eyes lower, more broadly rounded and more lateral in position; abdomen usually ending more bluntly. [Go to] 4
4b – These appendages [inferior abdominal appendages (paraprocts)] straight or nearly so. [Go to] 5
5b – No dorsal hooks on any abdominal segments. [Go to] 10
10a – Lateral spines of segment 9 much longer than its mid-dorsal length. [Go to] 11
11b – Lateral spines on 8 nearly as long as on 9. [Go to] 12
12b – Superior abdominal appendage (epiproct) shorter than inferiors [inferior abdominal appendages (paraprocts)]. Tramea BINGO!

p. 41, Key to the species of the genus Tramea
1a – Lateral spines of segment 8 directed straight to rearward; paraprocts longer than epiproct; two rows of spinules on upper surface of epiproct. carolina BINGO!

Copyright © 2016 Walter Sanford. All rights reserved.

Dragonhunter dragonfly exuvia

June 12, 2016

A Dragonhunter dragonfly (Hagenius brevistylus) exuvia was collected along the Little Patuxent River by Richard Orr, renowned expert on odonates of the mid-Atlantic region of the United States, during an Audubon Naturalist Society adult class and field trip to the Patuxent Research Refuge on 15 June 2014.

Dragonhunter [nymphs] crawl out of the river and often cling on wet wood or roots/vegetation. I have seen them on mud but they seem to like vegetation or wood to cling to during emergence. I took a photo…of a cast skin at the same area [where this specimen was collected]. Source Credit: Personal communication from Richard Orr.

The decision tree used to identify the exuvia as a member of the Gomphidae Family (Clubtails) is fairly simple and straightforward.

  • The specimen has a flat labium (not mask-like).
  • Antennae are either club-shaped or paddle-like (not thin and threadlike as in Aeshnidae).

Dragonhunter is the largest of North American clubtails; accordingly the large size and shape of a Dragonhunter exuvia is so distinctive that it is relatively easy to identify to the species level.

A Dragonhunter dragonfly (Hagenius brevistylus) exuviae collected along the Little Patuxent River, Patuxent Research Refuge, Laurel, Maryland USA.

Lateral view showing left side, facing forward (annotated).

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

Notice the large, paddle-like antennae. They remind me of ping pong paddles.

A Dragonhunter dragonfly (Hagenius brevistylus) exuviae collected along the Little Patuxent River, Patuxent Research Refuge, Laurel, Maryland USA.

Head-on view (annotated).

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

The large size and shape of Dragonhunter exuviae are key field markers.

A Dragonhunter dragonfly (Hagenius brevistylus) exuviae collected along the Little Patuxent River, Patuxent Research Refuge, Laurel, Maryland USA.

Dorsal view.

All clubtail nymphs/evuviae have a flat labium that doesn’t cover the face.

A Dragonhunter dragonfly (Hagenius brevistylus) exuviae collected along the Little Patuxent River, Patuxent Research Refuge, Laurel, Maryland USA.

Ventral view (annotated).

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

Tech Tips:

The following equipment was used to shoot the preceding photographs: Fujifilm X-T1 digital camera; Fujinon XF18-55mm (27mm-82.5mm, 35mm equivalent) zoom lens plus “Fotasy” brand 10mm extension tube; Fujifilm Shoe Mount Flash EF-42 (on-camera, in TTL mode); Nissin i40 external flash unit (off-camera, in SD mode). A snap-on plastic diffuser was used for each external flash.

Adobe Photoshop CC 2015 was used to annotate selected images.

Related Resources:

Copyright © 2016 Walter Sanford. All rights reserved.

Spangled Skimmer dragonfly (teneral male)

June 6, 2016

Spangled Skimmer dragonfly (Libellula cyanea) was spotted along Beaver Pond Loop Trail at Accotink Bay Wildlife Refuge (ABWR).

A Spangled Skimmer dragonfly (Libellula cyanea) spotted at Accotink Bay Wildlife Refuge, Fairfax County, Virginia USA. This individual is a teneral male.

20 MAY 2016 | ABWR | Spangled Skimmer (teneral male)

This individual is a teneral male, as indicated by its coloration and terminal appendages. As a mature male, his eyes will be dark bluish-black and blue pruinescence will cover its body (thorax and abdomen).

A Spangled Skimmer dragonfly (Libellula cyanea) spotted at Accotink Bay Wildlife Refuge, Fairfax County, Virginia USA. This individual is a teneral male.

20 MAY 2016 | ABWR | Spangled Skimmer (teneral male)

Tech Tips:

The first photo of the dragonfly was taken by looking through a “keyhole” in a thicket of vegetation. Two camera settings are critical for enabling this type of shot: Autofocus Mode (one-area-focusing, using center focus point); and Metering Mode (Spot).

Copyright © 2016 Walter Sanford. All rights reserved.


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