Posts Tagged ‘vestigial genitalia’

MYN – Hylogomphus adelphus exuvia (ventral)

May 1, 2020

The following Anisoptera exuvia — collected by Freda van den Broek on 10 June 2019 along the St. Croix River in Polk County, Wisconsin USA — is definitely a member of Family Gomphidae (Clubtails), probably Mustached Clubtail (Hylogomphus adelphus).

Ventral view

Notice the exuvia has a flat labium (prementum). There are lateral spines located on abdominal segments six through nine (S6-S9); the lateral spine on S9 is spinulose-serrate along the outer edge. Also notice the well-developed tibial burrowing hooks on its legs.

10 JUN 2019 | Polk County, WI | H. adelphus exuvia (ventral)

Male (vestigial genitalia)

Male odonates have two sets of sex organs: primary genitalia located on abdominal segment nine (S9); and secondary genitalia located on abdominal segments two-to-three (S2-3).

Both sets of vestigial genitalia are clearly visible on the ventral side of some (but not all) specimens, such as the H. adelphus exuvia shown above.

Related Resources

Tech Tips

This subject was photographed against a pure white background (255, 255, 255) using the “Meet Your Neighbours” (MYN) technique.

12 photos of the specimen were taken using an aperture of f/16; in-camera focus peaking was used to highlight select areas in each photo. A subset of six (6) photos and Adobe Photoshop CC 2017 were used to create- and annotate the focus-stacked composite image shown above.

Copyright © 2020 Walter Sanford. All rights reserved.

Post update: Aeshna umbrosa exuvia

January 8, 2020

Male odonates have two sets of sex organs: primary genitalia located on abdominal segment nine (S9); and secondary genitalia located on abdominal segments two-to-three (S2-3).

Closer examination of some test shots of the following Shadow Darner dragonfly (Aeshna umbrosa) exuvia, photographed on 02 December 2018, showed both sets of vestigial genitalia are clearly visible on the ventral side of this specimen.

Aeshna umbrosa (mating pair)

All odonates (dragonflies and damselflies) have a 10-segmented abdomen, numbered from front to back. Male dragonfly secondary genitalia, called hamules, are located in segments two and three (S2 and S3); female genitalia in segment eight (S8). Male and female dragonflies form the mating wheel in order for their genitalia to connect during copulation.

A. umbrosa (in wheel). Photo used with permission from Patrick Boez.

Related Resource: Test shots: Aeshna umbrosa exuvia.

Copyright © 2020 Walter Sanford. All rights reserved.


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