Posts Tagged ‘paraprocts’

Epitheca princeps exuvia

September 6, 2018

An odonate exuvia was collected by Michael Boatwright, founder and administrator of the Virginia Odonata Facebook group, on 07 June 2018 at Otter Lake in Amherst County, Virginia USA.

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 used to identify the exuvia as a member of the Family Corduliidae (Emeralds).

  • The specimen has a mask-like labium (prementum) that covers the face, as shown in Image No. 1, characteristic of four families of odonates: Cordulegastridae (Spiketails); Corduliidae (Emeralds); Libellulidae (Skimmers); and Macromiidae (Cruisers).
  • There is no horn on 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: It’s probably Corduliidae if the cerci are at least half as long as the paraprocts, as shown in Image No. 4. [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. 1Epitheca princeps | exuvia (face-head)

Step 2. Genus and species

Characters from two dichotomous keys were used to identify the genus and species: Prince Baskettail dragonfly (Epitheca princeps). See Epitheca princeps exuvia, another of my illustrated guides to identification of odonate exuviae, for a detailed explanation of the decision tree used to identify the genus and species of this specimen.

No. 2 | Epitheca princeps | exuvia (dorsal)

This individual is a male, as indicated by the vestigial hamuli visible on the ventral side of abdominal segments two and three (S2-3).

No. 3Epitheca princeps | exuvia (ventral)

Notice the cerci are at least half as long as the paraprocts, as shown in Image No. 4.

No. 4Epitheca princeps | exuvia (posterior abdomen)

Image No. 5 shows a dorsal-lateral view of the mid-dorsal hooks.

No. 5Epitheca princeps | exuvia (dorsal-lateral)

Look-alike species

I really wanted this specimen to be Stream Cruiser dragonfly (Didymops transversa). I think exuviae from D. transversa and E. princeps are similar in appearance — an opinion not shared by at least one expert on identification of odonate exuviae.

Two characters proved to be the deal-breaker that forced me to abandon D. tranversa in favor of E. princeps. 1) The specimen does not have a horn on its face-head. 2) This specimen is only 25 mm long (2.5 cm); D. transversa larvae/exuviae are 30 mm long (3.0 cm), according to Dragonflies of North America, Needham, James G., et al.

Tech Tips

The following equipment was used to shoot Image No. 1-5: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode.

Image No. 1-5 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017: Image No. 1 (7 photos); Image No. 2 (22 photos); Image No. 3 (19 photos); Image No. 4 (10 photos); Image No. 5 (20 photos).

Copyright © 2018 Walter Sanford. All rights reserved.

Advertisements

Post update: Phanogomphus lividus exuvia

April 13, 2018

Phanogomphus lividus exuvia, my identification guide for Ashy Clubtail exuviae, was updated to feature two new annotated high-magnification macro composite images.

  • Photo No. 1: The specimen was rehydrated/relaxed in order to reposition the front legs for an unobstructed view of the prementum, especially the median lobe of the labium.
  • Photo No. 2: A close-up view of the anal pyramid (terminal appendages) verified the “superior caudal appendage (epiproct) is as long as inferiors (paraprocts).”

The first image is a composite of six photos that shows a ventral view of the prementum.

Editor’s Note: Sincere thanks to Sue and John Gregoire for guiding me to the location of the median lobe.

The last image is a composite of 15 photos that shows a dorsal view of the abdomen; the inset image is a selection from a composite of 10 photos that shows a ventral view of the anal pyramid.

No. 2 | Ashy Clubtail (Phanogomphus lividus) | exuvia (anal pyramid)

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividusnymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuvia from the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

Tech Tips

The following equipment was used to shoot all of the photos for the preceding composite images: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for f/8 at either 2x or ~3x magnification); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode; and Canon 580 EX- and Canon 580EX II Speedlites in “Slave” mode.

Adobe Photoshop CC 2017 was used to create the composite image by “round-tripping” with Apple Aperture.

Copyright © 2018 Walter Sanford. All rights reserved.

Phanogomphus lividus exuvia

April 5, 2018

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividusnymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuvia from the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

A two-step process was used to verify the identity 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), as shown in Photo No. 1 and 3.
  • Antennae are club-like (not thin and thread-like, as in  Aeshnidae larvae), as shown in Photo No. 1.

It’s simple and straightforward to recognize this specimen is a clubtail.

No. 1 | Ashy Clubtail (Phanogomphus lividus) | exuvia (face-head)

Step 2. Genus and species

Lateral spines are present on abdominal segments six through nine (S6-S9).

The superior caudal appendage (epiproct) is as long as inferiors (paraprocts), as shown in Photo No. 4. The view of the terminal appendages is still slightly obscured by debris after the specimen was cleaned, making it challenging to distinguish the cerci from the paraprocts. Nonetheless, the epiproct and paraprocts appear to be nearly the same length.

The median lobe of the labium (prementum) is straight-edged, as shown in Photo No. 5.

After emergence

The next photograph shows the Ashy Clubtail dragonfly after emergence from one of Bob Perkins‘ holding tanks. Phanogomphus lividus is 48-56 mm in total length (Paulson, 2011).

Image used with permission from Bob Perkins.

This individual is a female, as indicated by its rounded hind wings and terminal appendages.

Image used with permission from Bob Perkins.

Related Resource

The dichotomous key for Gomphus (now Phanogomphus) that appears on p. 20 in Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, was used to attempt to verify the genus and species of the exuvia. Markers that match this specimen are highlighted in boldface green text. Three boldface green asterisks (***) are used to highlight the thread for identification of P. lividus. Disclaimers are highlighted in boldface red text.

1a. Lateral spines on abdominal segments 7 to 9 (very minute if present on 6). [2]
***1b. Lateral spines on abdominal segments 6 to 9 well developed. [3]

3a. Superior caudal appendage (epiproct) shorter than inferiors (paraprocts); Teeth on lateral lobes of labium obsolete or poorly developed. [quadricolor]
***3b. Superior caudal appendage (epiproct) as long as inferiors (paraprocts); Teeth on lateral lobes of labium well developed. [4]

***4a. Median lobe of labium straight-edged. [lividus]
4b. Median lobe of labium convex-edged. [5]


Note: The weakest aspect of this key is couplet 4, as it applies to Gomphus descriptus [Harpoon Clubtail], the difference in the “convexity” of the median lobe between lividus and descriptus being very slight and difficult to discern in practice. Donnelly (pers. comm.) has found that, at least with New York specimens, the posterior narrowing of the median lobe of the labium is more abrupt in livid, and relatively gradual in descriptus. Also, the labial teeth are better developed in livid than in descriptus. These characters are so relative that any unknown suspected of being either of these species should be compared to reference specimens.

Tech Tips

The following equipment was used to shoot Photo No. 2 and 3: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Photo No. 1, 4, and 5Canon MP-E 65mm Macro lens (manual focus only, set for either 2x or 3x magnification) plus the multiple-flash setup.

Photo No. 1-3 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017.

Bob Perkins’ photos were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

Boyeria vinosa exuvia

March 8, 2018

Bob Perkins collected and reared an unknown species of odonate nymph from a stream located in southwestern Virginia. The larva emerged from one of Bob’s holding tanks on 08 May 2017 and metamorphosed into an adult female Fawn Darner dragonfly (Boyeria vinosa). Fawn Darner is a member of the Family Aeshnidae (Darners).

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 Aeshnidae (Darners).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in Photo No. 1, 3, and 4.
  • Antennae are thin and thread-like (not club-like, as in Gomphidae larvae), as shown in Photo No. 1-4.
  • Eyes are large relative to the size of the head, as shown in Photo No. 1.

No. 1 | Boyeria vinosa | exuvia (face-head)

Step 2. Genus and species

The dichotomous key for Boyeria larvae that appears on p. 22 in Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, was used to verify the genus and species of the exuvia.

1. Length when grown 37-39 mm;
Lateral spines on abdominal segments 4 to 9 (minute on 4);
Mentum of labium more than twice as long as its median width;
Inferior caudal appendages (paraprocts) stouter, scarcely incurved at tips;
Apex of superior anal appendage (epiproct) uncleft and sharply pointed;
Epiproct as long as paraprocts. [grafiana]

1’. Length when grown 34-37 mm;
Lateral spines on abdominal segments 5 to 9;
Mentum of labium less than twice as long as its median width;
Inferior caudal appendages (paraprocts) more slender, distinctly incurved at tips;
Apex of superior anal appendage (epiproct) deeply emarginate (cleft);
Epiproct distinctly shorter than paraprocts. [vinosa]

The exuvia is ~35 mm (~3.5 cm) long. Lateral spines are present on abdominal segments five to nine (S5 to S9).

No. 2 | Boyeria vinosa | exuvia (dorsal)

The rudimentary ovipositor shown in Photo No. 3 indicates this individual is a female.

No. 3 | Boyeria vinosa | exuvia (ventral)

The prementum is less than twice as long as its median width, as shown in Photo No. 4.

No. 4 | Boyeria vinosa | exuvia (prementum)

The paraprocts are incurved at the tips.

No. 5 | Boyeria vinosa | exuvia (anal pyramid)

There is a cleft in the apex of the epiproct. The cleft is closed in the exuvia (above); it is open in the nymph (below). Both photos show the same specimen, before and after emergence.

Image used with permission from Bob Perkins.

Both the Soltesz dichotomous key and the key for Boyeria larvae that appears on pp. 88-89 in Dragonflies of North America, Third Edition by Needham et al. describe the epiproct as “distinctly shorter than paraprocts.” The epiproct and paraprocts are nearly the same length. In the opinion of the author, this marker is least useful for differentiating grafiana and vinosa nymphs/evuviae.

This specimen is confirmed as an exuvia from a Fawn Darner dragonfly (Boyeria vinosa).

Adult

The adult Fawn Darner dragonfly emerged on 08 May 2017. Fawn Darners are, on average, 60-71 mm long (Paulson, 2011).

Image used with permission from Bob Perkins.

This individual is a female, as indicated by its rounded hind wings (above) and prominent ovipositor (below).

Image used with permission from Bob Perkins.

Tech Tips

The following equipment was used to shoot Photo No. 2 and 3: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); and Canon MT-26EX-RT Macro Twin LitePhoto No. 1, 4, and 5: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 2x – 3x magnification); and Canon MT-26EX-RT Macro Twin Lite.

Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for all photos.

Adobe Photoshop CC 2017 was used to annotate selected images.

Bob Perkins’ photos were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens. The photos of the adult were taken soon after emergence.

Related Resource

The dichotomous key for Boyeria larvae that appears on pp. 88-89 in Dragonflies of North America, Third Edition by Needham et al. is as follows.

1. Epiproct about as long as paraprocts, its apex acute, not emarginate; greatest width of prementum about 3/5 its length; paraprocts shorter than abdominal segments 9+10, each with apex nearly straight (Fig. 85). [grafiana]

1’. Epiproct distinctly shorter than paraprocts, its apex distinctly emarginate; greatest width of prementum about 2/3 its length; paraprocts longer than abdominal segments 9+10, each with apex distinctly incurved (Fig. 85). [vinosa]

Post Update

Thanks to Northeast Odonata Facebook group members Curt Oien and Nick Block for sharing the following helpful tips. Both Curt and Nick are also members of the Dragonfly Society of the Americas.

The face-head of an Aeshnidae nymph/exuvia is relatively easy to recognize. Would I have said that when I was a beginner? In a word, no. Watch the Vimeo video a few times and you’ll see what I’m saying.

So, after you determine a specimen is from the Family Aeshnidae, look for a prominent light-colored diamond shape on the dorsal side of abdominal segment eight (S8), as shown in Photo No. 2 and 5: if it’s there, then you can be fairly certain the genus is Boyeria.

Curt looks for the cleft in the epiproct to determine the species. I recommend looking at other markers that are easier to see.

Copyright © 2018 Walter Sanford. All rights reserved.

Erpetogomphus designatus exuvia

February 28, 2018

Michael Powell collected several odonate exuviae during a photowalk along the Potomac River in Fairfax County, Virginia USA, including two damselflies and two dragonflies. The exact date is uncertain, although Mike thinks the exuviae were collected sometime between 19-23 July 2017.

A two-step process was used to identify the genus and species of one of the two dragonfly exuviae.

  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. 4.]
  • Antennae are club-like (not thin and thread-like, as in Aeshnidae). [See Photo No. 1.]
  • Eyes not exceptionally large compared to the size of the head (not large, as in Aeshnidae). [See Photo No. 1.]
(See a full-size version of the original photo, without annotation.)

Step 2. Genus and species

The dichotomous key for Erpetogomphus larvae that appears on pp. 156-157 in Dragonflies of North America, Third Edition by Needham et al. was used to identify the genus and species of the exuvia. The first couplet [1, 1′] is as follows.

1. Dorsal hooks well-developed on abdominal segments 2-9 (Fig. 183a) [2]
1’. Dorsal hooks absent or vestigial on abdominal segments 7-9 (Fig. 183c) (usually present on at least some of the more anterior segments [3]

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

A leap of faith is required to see the small dorsal hooks present on abdominal segments two through nine (S2 – S9), but they are there.

Notice the divergent wing pads. The white filaments that extend from the split in the thorax (as shown above) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

2(1). Lateral spines present on abdominal segments 6-9 only; femora with long, hair-like setae [designatus] [Eastern Ringtail]
2’. Lateral spines present on abdominal segments 5-9 only; femora without long, hair-like setae [constrictor] [Knob-tipped Ringtail]

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

The caudal appendages (terminal appendages) are all about the same length, a key marker for designatus.

Notice the flat labium that doesn’t cover the face, as shown in the following photo.

This specimen is tentatively identified as an exuvia from an Eastern Ringtail dragonfly (Erpetogomphus designatus). The exuvia that Mike Powell collected is similar in appearance to the following excellent photograph of an Erpetogomphus designatus nymph by Steve Krotzer, Haysop Hill Photography.

Image used with permission from Steve Krotzer.

Tech Tips

The following equipment was used to shoot Photo No. 2 and 4: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); and Canon MT-26EX-RT Macro Twin LitePhoto No. 1 and 3: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification); and Canon MT-26EX-RT Macro Twin Lite. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for some photos.

Adobe Photoshop CC 2017 was used to annotate selected images.

Copyright © 2018 Walter Sanford. All rights reserved.

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.

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.

Gomphurus vastus exuvia

February 17, 2017

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.

A Cobra Clubtail dragonfly (Gomphurus vastus) spotted at Riverbend Park, Fairfax County, Virginia USA. This individual is a male.

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.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

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.]
A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

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.]
A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

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. 5Cobra 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. 6Cobra 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.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

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.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) collected at Riverbend Park, Fairfax County, Virginia USA.

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.

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 Lumix 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.

A Cobra Clubtail dragonfly exuvia (Gomphurus vastus) photographed in situ at Riverbend Park, Fairfax County, Virginia USA.

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

Related Resources:

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.

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.


%d bloggers like this: