Anal pyramid

The “anal pyramid” is a more-or-less triangularly-shaped group of five appendages on the posterior end of dragonfly larvae (nymphs) and exuviae, including one epiproct, two cerci (sing. cercus), and two paraprocts.

The author suggests either “posterior pyramid” or “posterior triangle” as a less offensive sounding collective name for these anatomical parts. The author is just saying.

Eastern Ringtail (E. designatus) | exuvia (distal abdomen, dorsal view)

Although the anal pyramid isn’t always shaped like a perfect equilateral triangle, as shown above (in white), it always features the same five component body parts. These parts are often critical for identifying odonate larvae (nymphs) and exuviae.

Glossary

• cercus (pl. cerci) – Superior appendages; “Paired appendages at the tip of the abdomen.”; part of the anal pyramid, on either side of the epiproct. https://bugguide.net/node/view/114114
• epiproct – Superior caudal appendage; a single appendage at the center of the anal pyramid. https://bugguide.net/node/view/124493
• paraproct – Inferior appendages (lower pair) of the anal pyramid. https://bugguide.net/node/view/124491

 

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The Backstory

The Eastern Ringtail dragonfly (Erpetogomphus designatus) exuvia shown above was collected along the Potomac River at Riverbend Park, Fairfax County, Virginia USA. This species is a member of Family Gomphidae (Clubtails). I created a photo-illustrated identification guide for E. designatus using the same specimen.

Copyright © 2021 Walter Sanford. All rights reserved.

Tags: anal pyramid, Eastern Ringtail dragonfly, Erpetogomphus designatus, exuvia, Family Gomphidae (Clubtails), Signs of Wildlife