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
- MYN – Hylogomphus adelphus exuvia [face-head-dorsal]
- MYN – Hylogomphus adelphus exuvia (dorsal)
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.
Tags: BoG Photo Studio, Family Gomphidae (Clubtails), Hylogomphus adelphus, labium, lateral spines, male, Meet Your Neighbours, Mustached Clubtail dragonfly, studio photography, vestigial genitalia
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