Puzzle solved: Anax junius exuvia (female)

Identifying odonate exuviae is a lot like solving a jigsaw puzzle — eventually all of the puzzle pieces fit together to reveal a clear picture. As it turns out, while I’ve been experimenting with the “Meet Your Neighbours” technique for photographing natural subjects against a pure white background, I was also collecting puzzle pieces that would enable me to identify the dragonfly exuvia.

A two-step process was used to identify the genus and species of the specimen featured in my last two blog posts.

  1. Determine the family.
  2. Determine the genus and species.

Step 1. Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video, Identifying dragonfly larva to family (8:06). Here’s the decision tree I used to identify the exuvia as a member of the Family Aeshnidae (Darners).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in Photo No. 1.
  • Antennae are thin and thread-like (not club-like, as in Gomphidae larvae), as shown in Photo No. 1.
  • Eyes are large relative to the size of the head, as shown in Photo No. 1 and 4.

No. 1 | Common Green Darner (Anax junius) | exuvia (face-head)

Step 2. Genus and species

As shown in Photo No. 2 and 4, lateral spines along abdominal segments seven, eight, and nine (S7-9) indicate the genus is Anax.

No. 2 | Common Green Darner (Anax junius) | exuvia (ventral view)

At this point, you know the species could be either junius (Common Green Darner dragonfly) or longipes (Comet Darner dragonfly). The species is determined by the shape of the palpal lobes (part of the prementum) and the length of the specimen.

No. 3 | Common Green Darner (Anax junius) | exuvia (ventral view)

Notice the palpal lobes are rounded, as shown in Photo No. 3. The specimen is ~4.7 cm (~1.9 in) in length, not counting a slight bend in the body.

No. 4 | Common Green Darner (Anax junius) | exuvia (dorsal view)

The rounded shape of the palpal lobes (see Photo No. 3) plus the length of the specimen (see Photo No. 4) indicate the species is juniusAnax junius is one of the more common species of Aeshnidae found in Northern Virginia.

Finally, the rudimentary ovipositor shown in Photo No. 2 indicates this individual is a female.

Related Resource: Anax junius exuvia, another photo-illustrated identification guide by Walter Sanford.

Copyright © 2019 Walter Sanford. All rights reserved.

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