Anatomy of a male Tiger Spiketail

The following annotated image shows a Tiger Spiketail dragonfly (Cordulegaster erronea). This individual is a male, as indicated by his hamules, “indented” hind wings, and terminal appendages.

Hamules

Hamules? What are hamules?

hamules: paired structures that project from genital pocket under second segment and hold female abdomen in place during copulation Source Credit: Paulson, Dennis (2011-12-19). Dragonflies and Damselflies of the East (Princeton Field Guides) (Kindle Locations 11618-116198). Princeton University Press. Kindle Edition.

Male dragonfly secondary genitalia, called hamules, are located below abdominal segments two and three (S2 and S3), as shown in the following annotated image. Hamules come in a variety of sizes and shapes, but their function is identical for all species of odonates. Some species of dragonflies and damselflies — such as Ashy Clubtail versus Lancet Clubtail and Southern Spreadwing versus Sweetflag Spreadwing, to name a few — can be differentiated/identified with certainty only by examining the hamules under magnification.

Photo used with written permission from Michael Powell.

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

Indented hind wings

Male members of many families of dragonflies have “indented” hind wings near the body, with some notable exceptions.

Hind wing venation and shape can identify the sex of most dragonflies. Petaltails, darners (except Anax), clubtails, spiketails, cruisers, and some emeralds. Wing shape isn’t helpful to sex baskettails since they are largely the same. They are different in Cordulia, Dorocordulia, Somatochlora and to a lesser degree, Neurocordulia. Source Credit: Ed Lam, author and illustrator of Damselflies of the Northeast.

Terminal appendages

Identifying female versus male dragonflies and damselflies can be challenging but it’s a little easier when you know how to differentiate their terminal appendages.

All male dragonflies have three terminal appendages, collectively called “claspers,” that are used to grab and hold female dragonflies during mating: an upper pair of cerci (“superior appendages”) and a lower unpaired epiproct (“inferior appendage”). Male dragonfly terminal appendages don’t look exactly the same for all species of dragonflies, but their function is identical.

Generally speaking, spiketail dragonflies have relatively small terminal appendages. That said, they must get the job done!

Related Resource: Tiger Spiketail dragonfly (male) – a blog post by Walter Sanford.

Copyright © 2021 Walter Sanford. All rights reserved.

 

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One Response to “Anatomy of a male Tiger Spiketail”

  1. Wally Jones Says:

    Thank you, Walter, for a terrific summary on identification. For me, it sometimes takes adding several different characteristics to come up with an identification.

    Every little bit helps!

    And what a beautiful dragon is the Tiger Spiketail!

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