Dromogomphus spinosus exuvia

A dragonfly exuvia was collected by Joe Johnston on 22 May 2019 at Aquia Creek, Stafford County, Virginia USA. This specimen is the cast skin from a Black-shouldered Spinyleg (Dromogomphus spinosus) larva (nymph). D. spinosus is a member of Family Gomphidae (Clubtails).

At first I thought the exuvia might be a species from the genus Stylurus, based upon the mid-dorsal spine on abdominal segment nine (S9). After careful examination of two excellent photo-illustrated PowerPoint presentations by Kevin Hemeon at NymphFest 2016 (see Related Resources, below), I noticed none of the species in the genus Stylurus have dorsal hooks. That’s when I realized the specimen must be D. spinosus. Eureka!

Related Resources

The following PowerPoint presentations by Kevin Hemeon are available in the “Files” section of the Northeast Odonata Facebook group. Direct links to the documents are provided below.

Odonate Exuviae – a hyperlinked list of identification guides to many species of odonate exuviae from seven families of dragonflies and three families of damselflies.

The Backstory

Joe Johnston is an avid boater and sport fisherman who kindly agreed to be my “Eyes on the Aquia,” always on the lookout for odonate exuvia to share with me. On 22 May 2019 Joe caught a largemouth bass that swam around one of the wooden pilings of a boat dock that extends far into Aquia Creek. The fishing line was snagged on the piling so Joe moved his boat into position to free the fish. That’s when he noticed the exuvia clinging to a piling on the underside of the dock. Good catches, Joe!

Tech Tips

The following equipment was used to shoot the quick-and-dirty handheld macro photograph featured in this post: Fujifilm X-T1 digital camera; and Fujinon XF80mm macro lens plus lens hood. The camera was set for both manual exposure and manual focus. That’s right, a switch on the camera body is used to set the type of focus. It’s a Fujifilm thing. Actually, back-button focus was used to autofocus the image and adjusted manually as necessary. That’s also a Fujifilm thing. Camera settings: focal length 80mm (120mm, 35mm equivalent); ISO 200; f/9; 1/180s.

Godox XProF radio flash trigger, mounted on the hotshoe of my X-T1, was used to control an off-camera Godox TT685 Thinklite TTL Flash (TT685F) set for radio slave mode. The flash was fitted with a Lastolite Ezybox Speed-Lite 2 flash modifier.

Adobe Photoshop CC 2017 was used to spot-heal and sharpen the image, plus add annotations.

Sometime in the future (probably the odonate “off-season”) I will create higher quality composite images of this exuvia, shown from all viewpoints including the ventral view. As it turns out, the dorsal view is sufficient to identify this species.

Copyright © 2019 Walter Sanford. All rights reserved.

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