Lancet Clubtail dragonflies (males)

At least two Lancet Clubtail dragonflies (Phanogomphus exilis) were spotted during a photowalk along a mid-size stream in Fairfax County, Virginia USA.

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

These individuals are males, as indicated by their terminal appendages and indented hind wings.

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

The next photograph was taken at a later time than the first two photos. All of the photos in this post were taken near the same location. Is this another male, or the same one featured in the preceding photos? Who knows?

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

Lancet Clubtail versus Ashy Clubtail

Lancet Clubtail looks similar to Ashy Clubtail (Phanogomphus lividus). The only way to differentiate the two species with certainty is to examine their external reproductive anatomy; this is impossible unless the specimens are captured and examined in-hand.

Relative size is used sometimes to identify the two species: Lancet Clubtail is slightly smaller than Ashy Clubtail. There are two problems with this method of identification. First, it is virtually impossible to determine the exact size of a specimen in the field unless it is captured and measured. Second, some natural variation in size should be expected among individuals of the same species.

A quick-and-dirty method for differentiating Lancet- and Ashy Clubtails with some degree of certainty is to look at the markings on abdominal segments eight and nine (S8-9). Lancet Clubtail has a “spearpoint” on top of abdominal segment eight (S8) that almost reaches the end of the segment, a wide yellow stripe on top of segment nine (S9), and irregular yellow markings on the sides of segments eight and nine (S8-9).

03 MAY 2017 | Fairfax County, VA | Lancet Clubtail (male)

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

In contrast, Ashy Clubtail has a spearpoint on top of abdominal segment eight (S8) that is less than half the length of the segment, segment nine (S9) may or may not have a pale yellow stripe on top, and the sides of segments eight and nine (S8-9) may or may not have “poorly defined” yellow markings.

03 MAY 2017 | Fairfax County, VA | Ashy Clubtail (male)

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

Coloration is variable among individuals of the same species, so looking at abdominal markings isn’t always a reliable method of identification. In this case, it works beautifully.

Editor’s Note: The word “spearpoint” and the phrase “poorly defined” are descriptors attributed to Dennis Paulson, Dragonflies and Damselflies of the East (Princeton Field Guides). Princeton University Press. Kindle Edition.

Copyright © 2017 Walter Sanford. All rights reserved.

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One Response to “Lancet Clubtail dragonflies (males)”

  1. Lancet Clubtail dragonfly (male) | walter sanford's photoblog Says:

    […] Beaver Ponds,” Highland County, Virginia USA. This individual is a male, as indicated by his terminal appendages and “indented” hind […]

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