Posts Tagged ‘lateral spines’

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.

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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.

Epitheca princeps exuvia

March 5, 2017

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).

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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.

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

Dichotomous Key 2

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

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

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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.”

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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

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

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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.

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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

A Prince Baskettail dragonfly (Epitheca princeps) exuvia collected from an unknown location. This specimen is on temporary loan from Huntley Meadows Park, Fairfax County, Virginia USA.

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.

A Prince Baskettail dragonfly (Epitheca princeps) spotted at Mulligan Pond, Jackson Miles Abbott Wetland Refuge, Fairfax County, Virginia USA. This individual is a male, shown in flight.

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

Related Resources:

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.

Perithemis tenera exuviae

December 6, 2016

Several unknown dragonfly exuviae were collected on 07 July 2016 from the Potomac River, Fairfax County, Virginia USA; two of the specimens are featured in this post. A two-step process was used to identify the genus and species of the specimens.

Family

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

The exuviae have a mask-like labium (not flat) with smooth crenulations, indicating these individuals are members of Family Libellulidae (Skimmers).

Genus and species

A dichotomous key was used to tentatively identify the exuviae as Eastern Amberwing dragonfly (Perithemis tenera), as indicated by the following morphological characteristics.

  • The cerci (sing. cercus) are slightly less than half the length of the paraprocts.
  • Dorsal hooks are clearly visible on abdominal segments four through nine (S4-9), plus a “nub” that is visible on segment three (S3).
  • Lateral spines are clearly visible on abdominal segments eight and nine (S8-9).

These specimens are the first odonate exuviae that I was able to identify to the species level. Sincere thanks to Sue Gregoire, Kestrel Haven Migration Observatory, for verifying my preliminary observations and tentative identification.

No. 1

Each specimen is approximately 1.4 cm (~0.6″) in length and approximately 0.6 cm (~0.2″) in maximum width. In Photo No. 1, the specimen shown on the left is an emergent nymph that was stuck in its exuvia.

A pair of Eastern Amberwing dragonfly (Perithemis tenera) exuviae collected from the Potomac River, Dyke Marsh Wildlife Preserve, Fairfax County, Virginia USA.

No. 1 | Eastern Amberwing (Perithemis tenera) | exuviae (lateral, dorsal)

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

The white filaments that extend from the split in the thorax (as shown in Photo No. 1-3) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

No. 2

An Eastern Amberwing dragonfly (Perithemis tenera) exuvia collected from the Potomac River, Dyke Marsh Wildlife Preserve, Fairfax County, Virginia USA.

No. 2 | Eastern Amberwing (Perithemis tenera) | exuviae (dorsal)

No. 3

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

An Eastern Amberwing dragonfly (Perithemis tenera) exuvia collected from the Potomac River, Dyke Marsh Wildlife Preserve, Fairfax County, Virginia USA.

No. 3 | Eastern Amberwing (Perithemis tenera) | exuviae (head-on)

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

No. 4

One of the keys to identifying skimmer dragonflies to the species level is to carefully examine the anal pyramid (see S10, shown below), including the cerci (sing. cercus) and paraprocts. Notice the cerci are slightly less than half the length of the paraprocts.

An Eastern Amberwing dragonfly (Perithemis tenera) exuvia collected from the Potomac River, Dyke Marsh Wildlife Preserve, Fairfax County, Virginia USA.

No. 4 | Eastern Amberwing (Perithemis tenera) | exuviae (anal pyramid)

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

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 species of the dragonfly exuviae is as follows: 1b; 4b; 5a; 6a 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
5a – Dorsal hooks on some abdominal segments. [Go to] 6
6a – Dorsal hook on 9. Perithemis (One species, Perithemis tenera.) BINGO!

Copyright © 2016 Walter Sanford. All rights reserved.


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