I have photographed relatively few members of the Emerald Family of dragonflies. After tentatively identifying the following individual as a female Common Baskettail (Epitheca cynosura), I consulted the experts of the Northeast Odonata Facebook group for verification: I was fairly certain of the species; less certain of the gender.
Experienced odonate hunters like Chris Hill and Ed Lam looked at the specimen and quickly recognized its gender, as indicated by the cerci (terminal appendages) and thickness of its abdomen. In contrast, I haven’t seen enough baskettails to feel comfortable using those field marks to identify the gender.
So you may be wondering, “What was your first clue this individual is a female?” In a word (well, two) its subgenital plate, as shown in the following annotated image.
24 APR 2015 | Huntley Meadows Park | Common Baskettail (female)
A better view of the subgenital plate is provided by the following digital scan of the underside of the abdomen of a female Common Baskettail. The subgenital plate looks a little like a pair of calipers. Also known as vulvar lamina, the subgenital plate is located under the ninth abdominal segment (S9) of some female odonates and “serves to hold eggs in place during exophytic oviposition.” Remember that all dragonflies and damselflies have a 10-segmented abdomen, numbered from front to back.
Image used with permission from Ed Lam.
Related Resource: Common Baskettail dragonfly (male) – a tutorial illustrating male reproductive anatomy.
Editor’s Note: Special thanks to Chris Hill and Ed Lam, members of the Northeast Odonata Facebook group, for kindly confirming my tentative identification of the gender of this specimen and for teaching me about the subgenital plate (a.k.a., vulvar lamina) — a feature that I misidentified as an “ovipositor” in my initial post to the group.
Copyright © 2015 Walter Sanford. All rights reserved.
Tags: cerci, Common Baskettail dragonfly, Emerald Family, Epitheca cynosura, female, Huntley Meadows Park, subgenital plate, terminal appendages, vulvar lamina, wildlife photography
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