Posts Tagged ‘setal tuft’

Post update: Tachopteryx thoreyi exuvia

March 26, 2021

I just updated an older blog post in order to correct a label for an anatomical structure that was mislabeled, plus I added some new information.

The updated annotated image is shown below.

No. 2 | Gray Petaltail (Tachopteryx thoreyi) | exuvia (dorsal)

While I was editing the photo, I noticed something I hadn’t seen before — a large dorsal hook of abdominal segment nine (S9) that overhangs segment 10 (S10). This time I’m fairly sure the structure is correctly called a dorsal hook.

Related Resource: Tachopteryx thoreyi exuvia, an updated version of a blog post by Walter Sanford.

Copyright © 2021 Walter Sanford. All rights reserved.

Tachopteryx thoreyi exuvia

February 14, 2018

A Gray Petaltail dragonfly (Tachopteryx thoreyi) exuvia was collected on 28 May 2017 by Mike Boatwright in Amherst County, Virginia USA. Gray Petaltail is a member of the Family Petaluridae (Petaltails).

The exuvia has a flat labium, similar to members of the Family Aeshnidae (Darners) and Family Gomphidae (Clubtails). Its seven-segmented antennae are thick and club-like, similar to Clubtail dragonflies.

No. 1 | Gray Petaltail (Tachopteryx thoreyi) | exuvia (face-head)

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

The specimen is ~3.5 cm long and  ~1 cm wide. The wing pads extend to the end of abdominal segment five (S5), as shown in Photo No. 2.

The exuvia features two rows of “setal tufts” (hook-like structures) down its back.

[The] two rows that look like hooks are not hooks at all but rather stout, slight curved setae that are oriented vertically. Source Credit: Ken Tennessen, Western Odonata Facebook group.

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

Also notice a large dorsal hook of abdominal segment nine (S9) overhangs segment 10 (S10).

Photo No. 3 shows a ventral view of the exuvia. Notice the “rudimentary ovipositor” located on abdominal segment nine (S9). An ovipositor is used for egg-laying by all adult damselflies and some species of adult dragonflies: females have this feature; males do not. Therefore, this individual is a female Gray Petaltail.

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

The Backstory

Mike Boatwright has steadfastly resisted my best efforts to lure him to the dark side of odonate exuviae collection and identification. As a concession to me, Mike kindly agreed to look-out for exuviae in unusual habitats. As it turns out, the first exuvia Mike collected for me is a prized specimen. Perhaps I should have titled this post “Mike strikes gold in Virginia!”

Image used with permission from Mike Boatwright.

“Beginner’s luck?” Nope. I know from firsthand experience Mike Boatwright is an extraordinarily keen-eyed odonate hunter. Way to go, Mike!

Related Resources

The dichotomous key for Petaluridae larvae that appears on p. 320 in Dragonflies of North America, Third Edition by Needham et al. is as follows.

1. Antennae 6-segmented, 3rd and 5th segments longer than wide (Fig. 381); cerci each more than 1/2 as long as epiproct; lateral margins of abdominal segments 3-9 not expanded, lateral spines inconspicuous; western [Tanypteryx (p. 322)]
1’. Antennae 7-segmented, 3rd and 5th segments not longer than wide (Fig. 379); cerci each less than 1/2 as long as epiproct; lateral margins of abdominal segments 3-9 expanded, lateral spines conspicuous; eastern [Tachopteryx (p. 321)]

See also Test shots: Tachopteryx thoreyi exuviae, another blog post by Walter Sanford.

Tech Tips

The following equipment was used to shoot all of the preceding photographs: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tube; Canon 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.

Adobe Photoshop CC 2017 was used to annotate selected images.

Copyright © 2018 Walter Sanford. All rights reserved.


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