Posts Tagged ‘Appalachian Snaketail dragonfly’

Common Green Darner (male)

June 11, 2021

A Common Green Darner dragonfly (Anax junius) was observed during a photowalk with Michael Powell along a mid-size stream at an undisclosed location in Prince William County, Virginia USA.

While I was searching for the mythical Appalachian Snaketail dragonfly (Ophiogomphus incurvatus), Mike was tracking several Common Green Darners hawking flying insects over a large field near the stream. Thanks to Mike for giving me a heads-up when one of the darners landed in the field.

13 MAY 2021 | PNC. Wm. County | Common Green Darner (male)

This individual is a male, as indicated by his terminal appendages. Sometimes, as in this case, identifying sex can be challenging. Sexing Common Green Darner dragonflies is a blog post I created that illustrates several field marks can be used to identify the gender of female and male Anax junius.

The Backstory

I think the location that Mike and I visited provides the right habitat for Appalachian Snaketail dragonflies. Although we didn’t find the target species on the day of our visit I remain convinced O. incurvatus is there, waiting to be discovered.

Tech Tips

Notice the tips of the dragonfly’s cerci are near the bottom of the photo frame. I prefer to give the subject a little more “breathing room” but this image is the best one from the set of photos I shot and it is what it is — as close as I could get without spooking the dragonfly, albeit less than perfectly composed.

Copyright © 2021 Walter Sanford. All rights reserved.

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.

More composite images

March 24, 2018

Adobe Photoshop CC 2017 was used to create two simple two-image focus stacks. The composite images are perfectly in focus from head-to-tail.

Photo No. 1 is a composite image of two photos: one photo focused on the head; another photo focused on the anal pyramid.

No. 1 | 100mm | ISO 100 | f/22 | 1/500s | 0 ev

Photo No. 2 is a composite image of two photos: one photo focused on the prementum; another photo focused on the anal pyramid.

No. 2 | 100mm | ISO 100 | f/22 | 1/500s | 0 ev

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).

Tech Tips

The following equipment was used to shoot both photos in the composite image: 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 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.

Head-to-head, reprise

March 22, 2018

Head shots of an odonate exuvia from an Appalachian Snaketail dragonfly (Ophiogomphus incurvatus) were taken using two macro lenses: Canon EF100mm f/2.8L Macro lens (smallest aperture = f/32); Canon MP-E 65mm Macro lens (smallest aperture = f/16).

No. 1 | Canon EF 100mm Macro lens | f/22

Although there is more depth of field at f/22 than f/16, the more dramatic shot appears to be the one taken at higher magnification (2x) using the Canon MP-E 65mm Macro lens (shown below). Which photo do you prefer?

No. 2 | Canon MP-E 65mm Macro lens | f/16

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).

Tech Tips

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

Apple Aperture and Adobe Photoshop CC 2017 were used to edit both images.

Copyright © 2018 Walter Sanford. All rights reserved.


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