Posts Tagged ‘lateral spines’

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.

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Ophiogomphus incurvatus exuvia

March 26, 2018

Disclaimer

Soon after I began creating illustrated identification guides for odonate exuviae, I shared a pointer to Perithemis tenera exuviae on the Northeast Odonata Facebook group. Ed Lam commented on my post. The operative sentence is as follows.

I don’t expect anyone to identify Perithemis tenera larvae from Walter’s blog post but it gives a novice a better sense of what larval identification is all about and that has value. Source Credit: Ed Lam, Northeast Odonata Facebook group.

I disagree with Ed’s comment, although I let it go at the time in deference to Ed’s considerable expertise. I do expect anyone can use my guides to identify the species of odonate featured in each guide. Otherwise, what’s the point of making the guides? After I read Ed’s comment I tweaked the specific blog post and retooled the template that I use for most guides.

All of that being said, in my opinion it would be challenging at best to identify an exuvia from Ophiogomphus incurvatus to the species level using only the dichotomous key in Dragonflies of North America by Needham et al., the best resource currently available — significant sections of the key are unclear and unreliable. In contrast, Bob Perkins and I know the identity of the specimen because Bob observed the species of adult dragonfly that emerged from the exuvia.

For what it’s worth, this blog post features a fairly complete set of annotated photos of an Ophiogomphus incurvatus exuvia. Perhaps the photo set can be used in combination with the dichotomous key in order to make identification easier for others.

The Backstory

An Appalachian Snaketail dragonfly (Ophiogomphus incurvatus) nymph was collected by Bob Perkins. The nymph was reared in captivity until it emerged on 20 March 2017 and metamorphosed into an adult male. This specimen is the exuvia from the nymph. Appalachian Snaketail is a member of the Family Gomphidae (Clubtails).

A two-step process was used to attempt 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, 5, and 6.
  • 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. Expect a bumpy ride beyond this point!

No. 1 | Ophiogomphus incurvatus | exuvia (face-head)

Step 2. Genus and species

The size of specific antennal segments is a significant marker for identifying some species of Ophiogomphus. In this case, the antennae on the specimen will need to be cleaned in order to count segments and measure their dimensions.

No. 2 | Ophiogomphus incurvatus | exuvia (dorsal)

Lateral spines are present on abdominal segments seven through nine (S7-S9). Dorsal hooks appear to be well developed on segments eight and nine (S8, S9); they resemble “dorsal abdominal processes” on most other abdominal segments.

No. 3 | Ophiogomphus incurvatus | exuvia (dorsal-lateral)

The cerci are approximately three-fourths (3/4) as long as the epiproct and paraprocts.

No. 4 | Ophiogomphus incurvatus | exuvia (anal pyramid)

Photo No. 4 and 5 show ventral views of the exuvia.

No. 5 | Ophiogomphus incurvatus | exuvia (ventral)

The vestigial hamules shown in both photos indicate this individual is a male.

After emergence

The next photograph shows the Appalachian Snaketail dragonfly after emergence from one of Bob Perkins‘ holding tanks. Ophiogomphus incurvatus is 40-43 mm in total length (Paulson, 2011).

Image used with permission from Bob Perkins.

This individual is a male, as indicated by its “indented” hind wings, hamules, and terminal appendages.

Image used with permission from Bob Perkins.

Related Resource

The dichotomous key for Ophiogomphus that appears on pp. 261-262 in Dragonflies of North America, Third Edition by Needham et al. 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 O. incurvatus. Disclaimers are highlighted in boldface red text.

p. 261

1. Abdomen without lateral spines or dorsal hooks; antennal segment 4 minute, much narrower than segment 3. [howei]
***1’. Lateral spines present on abdominal segments 6 or 7-9; dorsal hooks usually well developed, if vestigial then antennal segment 4 more than 1/2 as wide as segment 3. [2]

2(1’). Antennal segment 4 more than 1/2 as wide as segment 3 (Fig. 319a); dorsal hooks on abdominal segments 2-9 low and blunt, or vestigial. [3]
***2’. Antennal segment 4 minute, much less than 1/2 as wide as segment 3; dorsal hooks normally prominent, usually hook-like, on at least some of abdominal segments 2-9 (sometimes low in O. carolus). [4]

p. 262

4(2’). Lateral spines on abdominal segments 6-9 (Fig. 323d). [5]
***4’. Lateral spines on abdominal segments 7-9 only. [6]

***6(4’). Dorsal hooks on abdominal segments 2-4 in lateral view usually less than 2/3 as high (measured from lowest point at intersegmental margin) as dorsal length of their respective tergites (along sclerotized, granulated cuticle only), in dorsal view with obtuse apices not extending backward beyond posterior border of tergite (Fig. 322a). [7*]
6’. Dorsal hooks on abdominal segments 2-4 in lateral view 2/3 as high, or more, (measured as above) as dorsal length of their respective tergites, in dorsal view with acute apices extending backward beyond posterior border of tergite (not beyond smooth intersegmental membrane; Fig. 322e). [14*]

***7(6). Antennal segment 3 not more than twice as long as wide. [8**]
7’. Antennal segment 3 is 2.3 to 3.0 times as long as wide. [10**]

***8(7). Antennal segment 3 is 1.7 to 1.8 times as long as wide; dorsal abdominal hooks highest and subequal on segments 2 or 3 to 4 or 5. [incurvatus**]
8’. Antennal segment 3 is 1.8 to 2.0 times as long as wide; dorsal abdominal hooks highest and subequal on segments 2 and 3 (Fig. 322a). [9**]


* Interpretation of this couplet in some individual cases may be ambiguous; if in doubt try both choices.
** Separation based on antennal measurements may be difficult in practice. Careful attention to shape of antennal segments (Fig. 319) should also help.

Tech Tips

The following equipment was used to shoot Photo No. 2, 3, and 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. Photo No. 1, 4, and 6Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification) plus the multiple-flash setup.

Adobe Photoshop CC 2017 was used to annotate Photo No. 1-6Photo No. 2, 4, 5, and 6 are focus-stacked composite images.

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.

Ophiogomphus aspersus exuvia

March 20, 2018

A Brook Snaketail dragonfly (Ophiogomphus aspersusnymph was collected by Bob Perkins on either 10 SEP 2017 or 03 OCT 2017 (the date is uncertain) along the New River in southwestern Virginia. The nymph was reared in captivity until it emerged on 31 OCT 2017 and metamorphosed into an adult female. The following specimen is the exuvia from the nymph. Brook Snaketail 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, 4, and 5.
  • Antennae are club-like (not thin and thread-like, as in  Aeshnidae larvae), as shown in Photo No. 1.

No. 1 | Ophiogomphus aspersus | exuvia (face-head)

Step 2. Genus and species

The dichotomous key for Ophiogomphus that appears on p. 262 in Dragonflies of North America, Third Edition by Needham et al. was used to verify the genus and species of the exuvia. The eleventh couplet [11, 11′] is as follows.

11(10). Lateral margins of prementum slightly convergent in distal 1/2 (Fig. 320c); lateral abdominal spines about 1/8 length of lateral margin of corresponding segment; in dorsal view, cerci about 2-1/2 times as long as basal width; dorsal hooks on abdominal segments 3-6 erect (Fig. 322d). [aspersus]

11’. Lateral margins of prementum parallel or slightly divergent in distal 1/2 (Fig. 320K); lateral abdominal spines each about 1/5 length of lateral margin of corresponding segment; in dorsal view, cerci each about twice as long as basal width; dorsal hooks on abdominal segments 3-6 appressed (Fig. 322d). [rupinsulensis]

No. 2 | Ophiogomphus aspersus | exuvia (dorsal)

The word “process,” as in “dorsal abdominal process,” is defined as follows.

An upstanding prominence, usually narrow and rod-like or spine-like. Source Credit: Glossary, Dragonflies of North America.

The dorsal hooks, a.k.a., dorsal abdominal processes, on abdominal segments three through six (S3-S6) are erect. Hey, call them whatever you like, including “erect” — there are raised bumps along most of the mid-dorsal abdomen, some of which are raised more noticeably than others, as shown in Photo No. 3.

No. 3 | Ophiogomphus aspersus | exuvia (dorsal-lateral)

The next two annotated images show ventral views of the exuvia.

No. 4 | Ophiogomphus aspersus | exuvia (ventral)

The flat labium doesn’t cover the face and the lateral margins of the prementum are slightly convergent in the distal half, as shown in Photo No. 5.

No. 5 | Ophiogomphus aspersus | exuvia (prementum)

Lateral spines are present on abdominal segments seven through nine (S7-S9) only. Did I measure the length of the lateral abdominal spines to see whether they are about one-eighth (1/8) the length of the lateral margin of the corresponding segment? In a word, no — the length looks about right to my unaided eye.

The cerci are about two-and-a-half (2-1/2) times as long as their basal width. Again, the length looks about right to my unaided eye.

No. 6 | Ophiogomphus aspersus | exuvia (anal pyramid)

The rudimentary ovipositor shown in Photo No. 4 and 7 indicates this individual is a female.

No. 7 | Ophiogomphus aspersus | exuvia (rudimentary ovipositor)

After emergence

The next photograph shows the Brook Snaketail dragonfly after emergence from one of Bob Perkins‘ holding tanks. Ophiogomphus aspersus is 44-49 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.

The last close-up photo shows a ventral view of the subgenital plate.

Image used with permission from Bob Perkins.

Tech Tips

The following equipment was used to shoot Photo No. 2-4: 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); 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 and 5-7: Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification) plus the multiple-flash setup.

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.

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.

Stylurus plagiatus exuvia

March 2, 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.

Both dragonfly exuviae are from the Family Gomphidae (Clubtails), as indicated by a flat labium that doesn’t cover the face as well as club-like antennae. The smaller specimen was identified as an Erpetogomphus designatus exuvia; this post describes the decision tree used to identify the larger specimen.

No. 1 | Stylurus plagiatus | exuvia (face-head)

Refer to Photo No. 2, 3, and 4. Notice that abdominal segment nine (S9) is elongated, strongly suggesting this individual is a member of the genus Stylurus.

The dichotomous key for Stylurus larvae that appears on pp. 310-312 in Dragonflies of North America, Third Edition by Needham et al. was used to identify the species of the exuvia. The ninth couplet [9, 9′] is as follows.

9(7’). Length of abdominal segment 9 at least equal to its basal width; lateral spines of abdominal segment 9 at least 1-1/2 times as long as those of segment 8; dorsal hook of segment 9 often large, in southern specimens overhanging segment 10; each labial palp with 3 teeth in addition to end hook; greatest width of prementum at least 4/5 its length. [plagiatus]
9’. Length of abdominal segment 9 less than its basal width; lateral spines of abdominal segment 9 no more than 1-1/2 times as long as those of segment 8; dorsal hook of segment 9 small, sometimes vestigial; labial palp with 2-3 teeth in addition to end hook; greatest width of prementum no more than 3/4 its length. [10]

Abdominal segment nine (S9) is slightly longer than its basal width, as shown in Photo No. 2. The lateral spines of segment nine (S9) are much longer than segment eight (S8).

No. 2 | Stylurus plagiatus | exuvia (dorsal)

Photo No. 3 shows a dorsal view of the distal abdomen. Notice the large dorsal hook of abdominal segment nine (S9) overhangs segment 10 (S10), a key marker for southern specimens of plagiatus. The dorsal hook couldn’t be seen before the exuvia was cleaned.

No. 3 | Stylurus plagiatus | exuvia (dorsal)

The flat labium doesn’t cover the face, as shown in Photo No. 4 and 5.

No. 4 | Stylurus plagiatus | exuvia (ventral)

Photo No. 5 shows a close-up of the prementum. Each labial palp features at least three (3) teeth in addition to the end hook. The greatest width of the prementum is approximately four-fifths (4/5) of its length.

No. 5 | Stylurus plagiatus | exuvia (prementum)

This specimen is confirmed as an exuvia from a Russet-tipped Clubtail dragonfly (Stylurus plagiatus).

The Backstory

Photo No. 6, featured in a recent blog post entitled Getting Started, is focused on abdominal segment nine (S9).

This specimen may need to be cleaned in order to see more clearly some key field markers used for identification.

No. 6 | Potomac River, Fairfax County, VA | odonate exuvia

The specimen was soaked in soapy water for at least 24 hours. A plastic spoon was used to scoop the exuvia from the water bath and transfer it to a dry plastic tray. Then a soft artist’s paintbrush was used to clean the exuvia, with extra attention on abdominal segment nine (S9). Two damselfly exuviae are soaking in the same water bath, shown below. Other useful tools include a magnifying glass and a plastic toothpick.

The odonate exuviae cleaning station at BoG Photo Studio.

The exuvia is pliable after soaking in water for at least 24 hours. After the specimen was cleaned, it was posed and allowed to dry for another day. The handle of a plastic spoon is a good drying rack that makes it easier to pose the legs. The Stylurus plagiatus exuvia is shown in the following photograph. The broken leg resting on the handle of the spoon was attached to the body only by spider web.

Stylurus plagiatus exuvia, posed on the handle of a plastic spoon.

Tech Tips

The following equipment was used to shoot Photo No. 1, 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. 3 and 5: 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.

A Panasonic Lumix DMC-FZ150 superzoom bridge camera was used to take photos of the odonate exuviae cleaning station.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources

Copyright © 2018 Walter Sanford. All rights reserved.

Stenogomphurus rogersi exuvia

February 24, 2018

Bob Perkins collected an unknown species of clubtail larva in February 2017 from a stream located in either Carroll- or Grayson County, Virginia USA. The larva emerged from one of Bob’s holding tanks on 13 March 2017 and metamorphosed into an adult female Sable Clubtail dragonfly (Stenogomphurus rogersi).

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 Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like). [See Photo No. 2.]
  • 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.)

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.

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.

The dichotomous key for Gomphidae larvae that appears on p. 233 in Dragonflies of North America, Third Edition by Needham et al. was used to verify the genus and species of the exuvia.

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

The first couplet [1, 1′] is as follows.

1. Median premental tooth lower than surrounding setae (Fig. 271b); small dorsal hooks present on abdominal segments 8 and 9; lateral spines present on segment 6 (Fig. 272) [rogersi]
1’. Median premental tooth as high as surrounding setae (Fig. 271a); dorsal hooks absent or vestigial on abdominal segments 8 and 9; lateral spines usually absent on segment 6 (Fig. 272) [consanguis]

The following annotated image shows a ventral view of the prementum. Notice the median premental tooth is lower than the surrounding setae.

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

The next annotated image shows a dorsal view of the distal abdomen. A leap of faith is required to see the small dorsal hooks present on abdominal segments eight and nine (S8, S9), but they are there. Also notice the lateral spines present on segment six (S6).

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

Therefore this specimen is confirmed as an exuvia from Stenogomphurus rogersi. Further, the rudimentary ovipositor shown in Photo No. 4 indicates this individual is a female.

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

Bonus Gallery

No. 5 | Sable Clubtail (Stenogomphurus rogersi) | exuvia (head-dorsal)

The Stenogomphurus rogersi exuvia is ~3.0 cm (~1.2 in) long.

No. 6 | Sable Clubtail (Stenogomphurus rogersi) | exuvia (dorsal-lateral)

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

Adult Sable Clubtail dragonflies are slightly larger, on average 4.7 – 5.0 cm (~1.9 – ~2.0 in) long.

Image used with permission from Bob Perkins.

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

Image used with permission from Bob Perkins.

Tech Tips

The following equipment was used to shoot Photo No. 1, 4, 5 and 6: 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 Lite. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for some photos. Photo No. 2 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.

Adobe Photoshop CC 2017 was used to annotate selected images.

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

Related Resource: Miraculous metamorphosis, a blog post featuring a head-to-head juxtaposition of the same exuvia and dragonfly that are the subjects in this post.

Copyright © 2018 Walter Sanford. All rights reserved.

Post update: Cordulegastridae exuvia

February 16, 2018

In a recent blog post entitled Cordulegastridae exuvia, I was able to identify the specimen to the family level. Since then, I was able to identify the genus and species.

The dichotomous key for Cordulegastridae larvae that appears on p. 330 in Dragonflies of North America, Third Edition by Needham et al. was used to identify the exuvia.

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

The first couplet [1, 1′] is as follows.

1. No lateral spines on abdominal segments 8-9; western [2]
1’. Lateral spines present on segments 8-9; eastern [3]

No. 1 | Cordulegaster sp. | exuvia (ventral)

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

Since the preceding annotated image shows lateral spines on abdominal segments eight and nine (S8, S9), proceed to the third couplet [3, 3′].

3(1’). Palpal setae 4; usually 5 large and 5 small premental setae present; some setae on margin of frontal shelf spatulate (Fig. 391e) [erronea]
3’. Palpal setae 5-7; 5-9 large and 3-5 small premental setae present; all setae on frontal shelf slender, not spatulate (Fig. 391f) [4]

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

The preceding annotated image shows the inner side of the prementum. Four (4) palpal setae are present, plus five (5) large- and five (5) small premental setae. The premental setae on the lower-right side of the prementum seem to be more intact than the ones on the upper-left: the large premental setae are labeled using white numerals; the small premental setae are labeled using red numerals.

The setae on the frontal shelf are mostly missing, as shown below. It’s possible they were broken off either when the larva burrowed in stream sediment (personal correspondence, Sue Gregoire) or when I cleaned the specimen.

No. 3 | Cordulegaster sp. | exuvia (frontal shelf)

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

Genus and species

The number of palpal setae strongly indicates the specimen is an exuvia from a Tiger Spiketail dragonfly (Cordulegaster erronea). Further, the rudimentary ovipositor shown in Photo No. 1 indicates this individual is a female.

The face behind the mask

Do you remember the way the female exuvia looked with its mask-like labium in place? In my opinion, she looked exotically beautiful!

No. 4 | Cordulegaster sp. | exuvia (face-head)

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

Well, that was then and this now. The following photo shows the face and mouth of the exuvia after the face mask was pulled away from the face in order to count the setae on the inner side of the prementum. Look closely at the full-size version of the photo. Yikes, that’s the stuff of nightmares!

No. 5 | Cordulegaster sp. | exuvia (face and mouth)

Tech Tips

The following equipment was used to shoot macro Photo No. 2, 3 and 5: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (set for 2x); 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.

The following equipment was used to shoot macro Photo No. 1 and 4Fujifilm X-T1 digital camera; Fujifilm MCEX-11 extension tube; and Fujinon XF80mm macro lens. An off-camera Fujifilm EF-X500 external flash unit and Sunpak LED-160 Video Light (with a white translucent plastic filter) were used for Photo No. 4. A Raynox DCR-250 close-up filter and Canon MT-26EX-RT Macro Twin Lite was used for Photo No. 1.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resource: Cordulegastridae exuvia, a blog post by Walter Sanford featuring an exuvia collected by Mike Boatwright.

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.

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.


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