Gomphus dilatatus in Virginia

On May 29, 2011, I found a female clubtail which I could not ID but which bore close resemblance to Gomphus vastas. I photographed the clubtail but did not collect a specimen. On June 1, 2011 I returned to photograph and compare a female Gomphus vastas with the unIDed gomphus found two days earlier. I was fortunate enough to find, photograph and collect females of both species. I have placed Vastas and Dilatatus side by side below for comparison.

Note the following differences:

Occiput concave in vastas and horizontal in dilatatus

Facial stripes clear and crisp in dilatatus and not as extensive

Two lateral thoracic stripes heavier and complete in dilatatus

S8 & S9 have more limited yellow in dilatatus

S7 appears to have more yellow forked posteriorily in limited comparison to vastas (subtle)

S9 not as broad (flared) and more laterally flattened in dilatatus

Subgenital plate bent in vastas and straight in dilatatus

Subgenital plate tapered in vastas and straight and forked at tip for dilatatus

In last series of photographs you can see that the dilatatus is heavier, longer (almost 3/8" to 1/2") than vastas

Gomphus vastas- Cobra Clubtail	Gomphus dilatatus- Blackwater Clubtail

On Friday, 2011 June 3, I caught a male Gomphus vastas and Gomphus dilatatus to provide a direct comparison between the two species. The two can be seen side by side below:

Gomphus dilatatus cerci Gomphus vastas cerci

Gomphus dilatatus genitalia

Gomphus dilatatus male- note longer terminal spine on femur Gomphus vastas- note longer last two spines on femur