Phanogomphus lividus exuvia

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividusnymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuvia from the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

A two-step process was used to verify the identity of the exuvia.

  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 used to identify the exuvia as a member of the Family Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in Photo No. 1 and 3.
  • Antennae are club-like (not thin and thread-like, as in  Aeshnidae larvae), as shown in Photo No. 1.

It’s simple and straightforward to recognize this specimen is a clubtail.

No. 1 | Ashy Clubtail (Phanogomphus lividus) | exuvia (face-head)

Step 2. Genus and species

Lateral spines are present on abdominal segments six through nine (S6-S9).

The superior caudal appendage (epiproct) is as long as inferiors (paraprocts), as shown in Photo No. 4. The view of the terminal appendages is still slightly obscured by debris after the specimen was cleaned, making it challenging to distinguish the cerci from the paraprocts. Nonetheless, the epiproct and paraprocts appear to be nearly the same length.

The median lobe of the labium (prementum) is straight-edged, as shown in Photo No. 5.

After emergence

The next photograph shows the Ashy Clubtail dragonfly after emergence from one of Bob Perkins‘ holding tanks. Phanogomphus lividus is 48-56 mm in total length (Paulson, 2011).

Image used with permission from Bob Perkins.

This individual is a female, as indicated by its rounded hind wings and terminal appendages.

Image used with permission from Bob Perkins.

Related Resource

The dichotomous key for Gomphus (now Phanogomphus) that appears on p. 20 in Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, was used to attempt to verify the genus and species of the exuvia. Field marks that match this specimen are highlighted in boldface green text. Three boldface green asterisks (***) are used to highlight the thread for identification of P. lividus. Disclaimers are highlighted in boldface red text.

1a. Lateral spines on abdominal segments 7 to 9 (very minute if present on 6). [2]
***1b. Lateral spines on abdominal segments 6 to 9 well developed. [3]

3a. Superior caudal appendage (epiproct) shorter than inferiors (paraprocts); Teeth on lateral lobes of labium obsolete or poorly developed. [quadricolor]
***3b. Superior caudal appendage (epiproct) as long as inferiors (paraprocts); Teeth on lateral lobes of labium well developed. [4]

***4a. Median lobe of labium straight-edged. [lividus]
4b. Median lobe of labium convex-edged. [5]

Note: The weakest aspect of this key is couplet 4, as it applies to Gomphus descriptus [Harpoon Clubtail], the difference in the “convexity” of the median lobe between lividus and descriptus being very slight and difficult to discern in practice. Donnelly (pers. comm.) has found that, at least with New York specimens, the posterior narrowing of the median lobe of the labium is more abrupt in livid, and relatively gradual in descriptus. Also, the labial teeth are better developed in livid than in descriptus. These characters are so relative that any unknown suspected of being either of these species should be compared to reference specimens.

Tech Tips

The following equipment was used to shoot Photo No. 2 and 3: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Photo No. 1, 4, and 5Canon MP-E 65mm Macro lens (manual focus only, set for either 2x or 3x magnification) plus the multiple-flash setup.

Photo No. 1-3 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017.

Bob Perkins’ photos were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

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4 Responses to “Phanogomphus lividus exuvia”

  1. P. lividus prementum | walter sanford's photoblog Says:

    […] exuvia. The composite is one of at least two new images that will be annotated and used to update Phanogomphus lividus exuvia, my identification guide for Ashy Clubtail […]

  2. Post update: Phanogomphus lividus exuvia | walter sanford's photoblog Says:

    […] Phanogomphus lividus exuvia, my identification guide for Ashy Clubtail exuviae, was updated to feature two new annotated high-magnification macro composite images. […]

  3. Test shots: “Generic Gomphid” | walter sanford's photoblog Says:

    […] identity of the specimen is Phanogompus sp. I see several similarities between this larva and a Phanogomphus lividus exuvia (Ashy Clubtail) in my collection, so Bob’s tentative identification might be correct. More […]

  4. Composite image: “Generic Gomphid” (face) | walter sanford's photoblog Says:

    […] Phanogomphus lividus exuvia […]

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