Epitheca cynosura exuvia

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.

No. 1 | Common Baskettail (Epitheca cynosura) | exuvia (face-head)

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

No. 2 | Common Baskettail (Epitheca cynosura) | exuvia (dorsal)

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).

No. 3 | Common Baskettail (Epitheca cynosura) | exuvia (face-head)

(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.

No. 5 | Common Baskettail (Epitheca cynosura) | exuvia (lateral)

(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.

No. 6 | Common Baskettail (Epitheca cynosura) | exuvia (face-head)

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.

• 1 Dorsal hooks present and well developed on some of the abdominal segments. [See Photo No. 4.] 2
• 2 Lateral spines on segment 8. [See Photo No. 7.] 3
• 3 Crenulations of labial palpi much shallower than a semicircle; … [See Photo No. 3.] 4
• 4 Lateral spines on segment 9 more than three times as long as those on segment 8, being at least as long as the mid-dorsal length of segment 9 and usually much longer. [See Photo No. 7.] = Epitheca (includes subgenera Epicordulia and Tetragoneuria)

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

• 1 Lateral spines of segment 9 pointing directly backward, their axes parallel. [See Photo No. 7.] 2
• 2 Lateral spines of segment 9 long, … [See Photo No. 7.] 4
• 4 Length of grown nymph about 22 mm. 5
• 5 Lateral spine of segment 9 about as long as mid-dorsal length of [S]9. [See Photo No. 7.] [premental setae not more than 10] = cynosura

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.

No. 8 | Common Baskettail (Epitheca cynosura) | exuvia (ventral)

(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:

• Vimeo video: Identifying dragonfly larva to family (8:06)
• Anatomy of a Dragonfly Larva, annotated illustration courtesy Jay Smith
• Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz: Alternate Key to the Genera of the Family Corduliidae, p. 29; Key to the species of the genus (subgenus) Tetragoneuria, p. 32.
• Odonate Exuviae, by Walter Sanford

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.

Macromia illinoiensis exuvia

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.

Identification Keys to Northeastern Anisoptera Larvae

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:

• Vimeo video: Identifying dragonfly larva to family (8:06)
• Anatomy of a Dragonfly Larva, annotated illustration courtesy Jay Smith
• Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz: Key to the Genera of the Family Macromiidae, page 27.
• Swift River Cruiser on exuvia – Macromia illinoiensis – Male, by Matthew J. Ryan
• Odonate Exuviae, by Walter Sanford

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

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.

• Zygoptera – Damselflies, Odonata Nymphs of Michigan, by Ethan Bright and Mark F. O’Brien
• Identification Manual for the Damselfly Nymphs (Zygoptera) of Florida, by Johnny S. Richardson
• Caudal Lamellae of Carolina Zygoptera, by Lynn Erckmann

Copyright © 2017 Walter Sanford. All rights reserved.

Epitheca princeps exuvia

The following Prince Baskettail dragonfly (Epitheca princeps) exuvia, on temporary loan from a friend, had been identified before I borrowed the specimen. A two-step process was used to verify the genus and species of the exuvia.

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 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. 4.]: 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).

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

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

Step 2. Genus and species

Characters from two dichotomous keys were used to identify the genus and species for the exuvia. Although palpal/mental setae were not examined, all other characters match Epitheca princeps.

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

Dichotomous Key 1

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

Key to the Families of Anisoptera, page 5.

• 6 Lateral caudal appendages (cerci) generally more than half as long as inferior appendages (paraprocts) [fig. 12] [See Photo No. 4.]; lateral spines of segment 9 longer than its mid-dorsal length [fig. 13] [See Photo No. 4.]; mid-dorsal hooks on abdomen often cultriform [fig 14] [See Photo No. 3.] Corduliidae

Key to the Genera of the Family Corduliidae, page 28.

• 1 Pair of small tubercles on top of head [See Photo No. 1.]; lateral lobe of labium with 4 or 5 setae… 2
• 2 Lateral spines of abdominal segment 8, if divergent at all, much weaker than those of 9; small setae on middle lobe of mentum numerous. Epicordulia (One species, Epicordulia princeps) [Editor’s Note: Epicordulia was previously considered to be a subgenera of Epitheca.]

Dichotomous Key 2

Corduliidae Selys – Emeralds, Odonata Nymphs of Michigan, by Ethan Bright and Mark F. O’Brien, UMMZ-Insect Division.

• 1b. Mid-dorsal hooks present, well-developed on some abdominal segments (picture) [See Photo No. 3.] – 4
• 4b. With lateral spines on Ab8 [See Photo No. 4.] – 5
• 5b. Crenulations on distal margin shallower than semicircle (picture) [See Photo No. 1.]; lateral spines on Ab9 equal or longer than those on Ab8, those on Ab8 not divergent (fig) [See Photo No. 4.] – 6
• 6a(5b). Lateral spines on Ab9 at least 2.0x as long as those on Ab8, at least equal to mid-dorsal length of Ab9 [See Photo No. 4.] – Epitheca

Epitheca Burmeister, 1839 (Corduliidae) – Baskettails

• 1a. Distal half of dorsal surface of prementum heavily setose; palpal setae usually 4, rarely 5(Fig. 2) – Subgenus Epicordulia, E. princeps

More annotated images

No. 2 | Prince Baskettail (Epitheca princeps) | exuvia (dorsal)

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

“Mid-dorsal hooks present, well-developed on some abdominal segments.”

No. 3 | Prince Baskettail (Epitheca princeps) | exuvia (dorso-lateral)

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

“With lateral spines on Ab8 [S8].” “Lateral spines on Ab9 [S9] at least 2.0x as long as those on Ab8 [S8], at least equal to mid-dorsal length of Ab9 [S9].” The cerci are at least half as long as the paraprocts.

No. 4 | Prince Baskettail (Epitheca princeps) | exuvia (anal pyramid)

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

Photo No. 5 shows a wider view of the ventral side of the specimen.

No. 5 | Prince Baskettail (Epitheca princeps) | exuvia (ventral)

Photo No. 6 shows a zoomed-in view of the prementum.

No. 6 | Prince Baskettail (Epitheca princeps) | exuvia (prementum)

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

Photo No. 7 shows another view of the prementum.

No. 7 | Prince Baskettail (Epitheca princeps) | exuvia (prementum)

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 and a Raynox DCR-250 close-up filter; 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.

A Canon Extender EF 1.4x II was used for more magnification in Photo No. 4, 6, 7 and 9. Adding the tele-extender results in a 1 f/stop loss of light; 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 annotate selected images.

Photo No. 8 and 9 show early work to get a good shot of the face-head, before Photo No. 1 emerged as the clear winner. I prefer Photo No. 1 because it provides the best view of the face-head, has the best composition and exposure, plus I like the way the exuvia seems to be floating in mid-air.

No. 8 | Prince Baskettail (Epitheca princeps) | exuvia (face-head)

No. 9 | Prince Baskettail (Epitheca princeps) | exuvia (face-head)

Although I have never seen a perching adult Prince Baskettail dragonfly, I was fortunate to shoot the following photo of a male in flight, featured in the blog post Changing of the guard.

No. 10 | 14 JUN 2016 | JMAWR | Prince Baskettail (male, in flight)

Related Resources:

• Vimeo video: Identifying dragonfly larva to family (8:06)
• Anatomy of a Dragonfly Larva, annotated illustration courtesy Jay Smith
• Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz: Key to the Families of Anisoptera, page 5; Key to the Genera of the Family Corduliidae, page 28.
• Odonata Nymphs of Michigan, by Ethan Bright and Mark F. O’Brien, UMMZ-Insect Division: Corduliidae Selys – Emeralds; Epitheca Burmeister, 1839 (Corduliidae) – Baskettails.
• Odonate Exuviae, by Walter Sanford

Copyright © 2017 Walter Sanford. All rights reserved.

Buddha

I found Buddha, in this case, the version known as “Happy Buddha.” (Notice the exuvia seems to be smiling.) I think I’ll rub Buddha’s belly to see whether it brings me good luck, prosperity and wealth.

Prince Baskettail dragonfly (Epitheca princeps) exuvia (ventral)

But seriously folks, this is a photo of a Prince Baskettail dragonfly (Epitheca princeps) exuvia on temporary loan. The date and location where the specimen was collected is unknown. More photos of this exuvia (including several annotated images) will be published in an upcoming post.

The following photo is the original. The preceding photo was cropped and rotated clockwise 90-degrees.

Prince Baskettail dragonfly (Epitheca princeps) exuvia (ventral)

Copyright © 2017 Walter Sanford. All rights reserved.

More power!

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.

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.

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:

• Sample macro photos taken using the equipment featured in this blog post. For details, see the section entitled “Tech Tips.”
• Odonate Exuviae, by Walter Sanford
• Montage of accidents from Home Improvement. (Just for fun. More power isn’t always a good thing!)

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.

Gomphurus vastus exuvia

10s, maybe 100s of adult Cobra Clubtail dragonflies (Gomphurus vastus) were spotted on 16 May 2016 during a photowalk along the Potomac River at Riverbend Park, Fairfax County, Virginia USA. Cobra Clubtails were the only species of odonate observed in a period of several hours.

No. 1 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (adult male)

A single exuvia (shown below) from an unknown species of dragonfly was collected with permission from park staff. If adult Cobra Clubtail dragonflies were common, then the specimen is probably a Cobra Clubtail exuvia, right? Let’s test our hypothesis.

No. 2 | Cobra Clubtail (Gomphurus vastus) | exuvia (face-head)

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

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 Gomphidae (Clubtails).

• The specimen has a flat labium that doesn’t cover the face (not mask-like). [See Photo No. 3.]
• Antennae are club-like (not thin and thread-like, as in Aeshnidae). [See Photo No. 3.]
• Eyes not exceptionally large compared to the size of the head (not large, as in Aeshnidae). [See Photo No. 3.]

No. 3 | Cobra Clubtail (Gomphurus vastus) | exuvia (face-head)

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

Step 2. 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.

Characters from two dichotomous keys were used to identify the exuvia, in part, due to confusion caused by the fact that the name for the genus to which Cobra Clubtail belongs was changed recently from Gomphus to Gomphurus. As a result, the workflow for identifying this specimen was a little “jumpier” than usual.

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

Dichotomous Key 1

Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz. Cobra Clubtail (Gomphus vastus), p. 15, Key to the species of the genus Gomphurus.

• 1a – Strongly hooked palpal lobes with few teeth (3-5). Gomphurus group I (2) [See Photo No. 8.]
• 2a – Length 27-30 mm. (vastus) [See Photo No. 4, below.]

No. 4 | Cobra Clubtail (Gomphurus vastus) | exuvia (dorsal)

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

Dichotomous Key 2

“Gomphus complex” (= Gomphini) – Clubtails, Odonata Nymphs of Michigan.

• 1b. Middorsal length of Ab9 [S9] less than half its basal width (fig); length of Ab10 [S10] < 0.50x its width (fig) – 6 [See Photo No. 6.]
• 6b. Lateral spines of Ab9 close to Ab10, markedly longer than those on Ab8 (fig) [S8]; abdomen appears dorsoventrally flattened (fig) – Gomphurus, 8 [See Photo No. 6.]
• 8b. Apical margin of median lobe of prementum straight or slightly convex (fig) – 9 [See Photo No. 8.]
• 9a.(8b). End hook of lateral lobe of labium strongly incurved, extending far past apex of the truncate, 3 to 4 lateral teeth next to it (fig) – Gomphurus vastus

No. 5 | Cobra Clubtail (Gomphurus vastus) | exuvia (posterior)

The preceding photograph shows a wider view of the posterior end of the abdomen. A closer view of the anal pyramid helps to illustrate several of the morphological characters described in Dichotomous Key 2.

No. 6 | Cobra Clubtail (Gomphurus vastus) | exuvia (anal pyramid)

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

The basal width of abdominal segment nine (S9) was measured in a straight line from edge-to-edge across the abdomen. The same distance would be longer if it were measured along the joint between abdominal segments eight and nine (S8 and S9). Either way the basal width is measured, the middorsal length is less than half of the basal width.

Since the middorsal length of abdominal segment 10 (S10) is clearly less than its basal width, the character wasn’t illustrated in the preceding annotated image.

Looking carefully at the anal pyramid, notice the cerci (sing. cercus) are slightly shorter than the epiproct, and the epiproct is almost as long as the paraprocts.

No. 7 | Cobra Clubtail (Gomphurus vastus) | exuvia (ventral)

Photo No. 7 shows a wider view of the ventral side of the specimen. Zooming in on the prementum helps to illustrate some of the morphological characters described in Dichotomous Key 2.

No. 8 | Cobra Clubtail (Gomphurus vastus) | exuvia (prementum)

(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, 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.

A Raynox DCR-250 close-up filter was used for Photo No. 3, 6, and 8. A Canon Extender EF 1.4x II was used for more magnification in Photo No. 8. Adding the tele-extender results in a 1 f/stop loss of light; 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 annotate selected images.

The following photograph of another dragonfly exuvia was taken in-situ along the shoreline of the Potomac River using a Panasonic DMC-FZ150 superzoom bridge camera and Canon 580EX Speedlite, my go-to kit for photowalking. There were many exuviae clinging to the concrete retaining wall shown in the photo. Photo No. 1 was taken using the same camera-flash combo.

No. 9 | 16 MAY 2016 | Riverbend Park | Cobra Clubtail (exuvia, in situ)

Related Resources:

• Vimeo video: Identifying dragonfly larva to family (8:06)
• Anatomy of a Dragonfly Larva, annotated illustration courtesy Jay Smith
• Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz. Key to the Genera of the Family Aeshnidae, p. 21; Key to the species of the genus Anax, p. 22.
• “Gomphus complex” (= Gomphini) – Clubtails, Odonata Nymphs of Michigan.
• Odonate Exuviae, by Walter Sanford

Editor’s Note: Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for her kind mentorship. Sue patiently provides guidance regarding the scientific jargon that can make it either challenging (at best) or impossible to understand many dichotomous keys for the identification of odonate larvae/exuviae. Like every good teacher, Sue doesn’t “give me a fish” — she teaches me how to fish. Thanks again, Sue!

Copyright © 2017 Walter Sanford. All rights reserved.

Anax junius exuvia

A dragonfly exuvia from the Family Aeshnidae (Darners) was collected on 21 June 2016 at Hidden Pond, Meadowood Recreation Area, Fairfax County, Virginia USA. This specimen is an exuvia from a Common Green Darner dragonfly (Anax junius).

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 I used to identify the exuvia as a member of the Family Aeshnidae (Darners).

• The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in Photo No. 1-4.
• Antennae are thin and thread-like (not club-like, as in Gomphidae larvae), as shown in Photo No. 4.
• Eyes are large relative to the size of the head, as shown in Photo No. 5.

Step 2. Genus and species

As shown in Photo No. 1, lateral spines along abdominal segments seven, eight, and nine (S7-9) indicate the genus is Anax.

No. 1 | Common Green Darner (Anax junius) | exuvia (dorsal-lateral)

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

At this point, you know the species could be either anax (Common Green Darner dragonfly) or longipes (Comet Darner dragonfly). The species is determined by the shape of the palpal lobes (see Photo No. 3) and the length of the specimen (see Photo No. 2).

No. 2 | Common Green Darner (Anax junius) | exuvia (lateral)

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

The labium, also known as the mentum, is 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 specimen is ~4.7 cm (~1.9 in) in length, not counting the bend in the body.

No. 3 | Common Green Darner (Anax junius) | exuvia (labium, ventral)

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

The rounded shape of the palpal lobes (see Photo No. 3, above) plus the length of the specimen (see Photo No. 2) indicate the species is junius. Anax junius is one of the more common species of Aeshnidae found in Northern Virginia.

No. 4 | Common Green Darner (Anax junius) | exuvia (face-head)

Notice the antennae are thin and thread-like, as shown in the preceding photo. If you are an aquatic animal, this is a face you don’t want to see up-close and personally!

No. 5 | Common Green Darner (Anax junius) | exuvia (head, dorsal)

The eyes are large relative to the size of the head.

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); 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. A Raynox DCR-250 close-up filter was used for Photo No. 3-5.

Adobe Photoshop CC 2017 was used to annotate selected images.

The first test shot for this exuvia was photographed using my Canon EF100mm f/2.8L Macro lens plus a Kenko 20mm macro automatic extension tube. As you can see in the following photo, the subject barely fit within the frame. Although the composition isn’t ideal, the resulting photo is dramatic nonetheless! The 20mm extension tube wasn’t used for the rest of the photo set.

No. 6 | Common Green Darner (Anax junius) | exuvia (lateral)

The following photograph of the exuvia was taken in-situ along the shoreline of Hidden Pond using a Panasonic DMC-FZ150 superzoom bridge camera and Canon 580EX Speedlite, my go-to kit for photowalking.

No. 7 | 21 JUN 2016 | MRA | Anax junius exuvia (in-situ)

Related Resources:

• Vimeo video: Identifying dragonfly larva to family (8:06)
• Anatomy of a Dragonfly Larva, annotated illustration courtesy Jay Smith
• Dragonfly hunting mosquito larvae and fishes (#221) (1:38)
• Odonate Exuviae, by Walter Sanford
• Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz. Key to the Genera of the Family Aeshnidae, p. 21; Key to the species of the genus Anax, p. 22.

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. 21, Key to the genera of the Family Aeshnidae
1b – Hind angles of head rounded … . (5)
5a – Lateral spines on abdominal segments 7 to 9 only. (6)
6b – Antenna about half as long as this distance [from the base of the antennae to the rear of head]. (Anax)

p. 22, Key to the species of the genus Anax
1a – Lateral lobes of labium tapering to a hooked point; total length about 40 mm. (junius) [Note: The total length of longipes is about 55 mm.]

Copyright © 2017 Walter Sanford. All rights reserved.

Stylurus spiniceps exuvia

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.

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).

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).

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.

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

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:

• Vimeo video: Identifying dragonfly larva to family (8:06)
• Anatomy of a Dragonfly Larva, annotated illustration courtesy Jay Smith
• Odonate Exuviae, by Walter Sanford
• Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz. Key to the Genera of the Family Gomphidae, p. 7; Key to the species of the genus Stylurus, p. 17.

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.

Top 10 Photos of 2016

The following gallery shows 33 finalists for my “Top 10 Photos of 2016.” The photos are presented in reverse-chronological order beginning in December 2016 and ending in May 2016.

The Top 10 photos will be selected using reader feedback. Please enter a comment at the end of this post listing the number for each of your 10 favorite photos. If listing 10 photos is asking too much, then please list at least five photos, e.g., No. 5, 8, 14, 17, 21, etc. Thanks for sharing your selections, and thanks for following my photoblog!

No. 1

The following specimen was collected on 16 May 2016 (with permission from park staff) along the Potomac River at Riverbend Park, Fairfax County, Virginia USA. (This studio photograph, taken on 25 December 2016, hasn’t been published in a post.)

16 MAY 2016 | Riverbend Park | Gomphurus vastus exuvia

No. 2

The next specimen was collected on 07 July 2016 along the Potomac River in Fairfax County, Virginia USA. (This studio photograph was taken on 02 December 2016.)

07 JUL 2016 | Potomac River | Eastern Amberwing (exuvia, head-on)

No. 3

06 NOV 2016 | Huntley Meadows Park | Great Spreadwing (female)

No. 4

14 OCT 2016 | JMAWR | Shadow Darner (female heteromorph)

No. 5

14 OCT 2016 | JMAWR | Russet-tipped Clubtail (male)

No. 6

10 OCT 2016 | Huntley Meadows Park | Black Saddlebags (male)

No. 7

27 SEP 2016 | MNWP | Southern Spreadwing (male)

No. 8

27 SEP 2016 | Mason Neck West Park | Wandering Glider (female)

No. 9

22SEP2016 | Huntley Meadows Park | Great Spreadwing (male)

No. 10

21 SEP 2016 | OBNWR | Hummingbird Clearwing moth (H. thysbe)

No. 11

15 SEP 2016 | Huntley Meadows Park | Wheel Bug (Arilus cristatus)

No. 12

15 SEP 2015 | JMAWR | Blue-faced Meadowhawk (female andromorph)

No. 13

12 SEP 2016 | HMP | Blue-faced Meadowhawk (male)

No. 14

08 AUG 2016 | Riverbend Park | Black-shouldered Spinyleg (female)

No. 15

04 AUG 2016 | Riverbend Park | Black-shouldered Spinyleg (male)

No. 16

04 AUG 2016 | Riverbend Park | Eastern Ringtail (female)

No. 17

04 AUG 2016 | Riverbend Park | American Rubyspot (female)

No. 18

15 JUL 2016 | Huntley Meadows Park | Halloween Pennant (female)

No. 19

15 JUL 2016 | HMP | Needham’s Skimmer (mature male)

No. 20

15 JUL 2016 | Huntley Meadows Park | Spot-winged Glider (female)

No. 21

11 JUL 2016 | OBNWR | Halloween Pennant (female)

No. 22

06 JUL 2016 | MRA | Halloween Pennant (young male)

No. 23

02 JUL 2016 | MRA | Carolina Saddlebags (male)

No. 24

26 JUN 2016 | JMAWR | Swift Setwing (male)

No. 25

26 JUN 2016 | JMAWR | Banded Pennant (male)

No. 26

24 JUN 2016 | HMP | Slender Spreadwing (adult male)

No. 27

24 JUN 2016 | HMP | Slender Spreadwing (mating pair, “in heart“)

No. 28

21 June 2016 | Dragonhunter dragonfly (female)

No. 29

18 JUN 2016 | OBNWR | Calico Pennant (female)

No. 30

18 JUN 2016 | OBNWR | Calico Pennant (male)

No. 31

08 JUN 2016 | Wickford Park | Common Sanddragon (male)

No. 32

26 MAY 2016 | Huntley Meadows Park | Painted Skimmer (teneral male)

No. 33

16 MAY 2016 | Riverbend Park | Cobra Clubtail (female)

Editor’s Note: The following location codes are used in some photo captions, shown above.

• HMP = Huntley Meadows Park
• JMAWR = Jackson Mile Abbott Wetland Refuge (#24 on the map)
• MNWP = Mason Neck West Park
• MRA = Meadowood Recreation Area
• OBNWR = Occoquan Bay National Wildlife Refuge
• WP/DC = Wickford Park/Dogue Creek

Copyright © 2016 Walter Sanford. All rights reserved.