Cobra Clubtail transforming to adult

Cobra Clubtail, Gomphus vastus, is one of those dragonfly species which stages a mass emergence. The entire adult population emerges from the Potomac River over the course of two weeks. Below is a live larva, or nymph, which has crawled onto the river bank moments before. It has spent two or more years in the river, burrowing in fine silt.

Below, another individual has climbed six feet up a tree trunk to shed its larval skin. This sequence took about one half hour. The larva is little over an inch long, the adults a little over two inches long.

The individual below, still weak and colorless, has just made its first flight. It will soon become black and bright yellow. After several days the yellow will change to dull green. The adults spend their first days feeding in fields near the river. When they are ready to breed they spend most of their time perched in trees or patrolling far out over the river, and become difficult to observe. The adults emerge in mid MAY. Most are gone by mid JULY. Rarely a few survive until early AUG.