An ecological classification of dragonfly species into spring and summer types was proposed by Corbet (1954). Much of the basis for the classification rests with the pattern and period of adult emergence. Since little information of this type is known for North American species, the following observations are reported.

On May 20, 1962, I spent several hours collecting Baisaeschna janata and Didymops transversa along the New River, two miles north of McCoy, Virginia. A search was made at that time for odonate exuviae. None were found. I returned to the site at 9:30 a.m. the following day. The vegetation, tree trunks, rocks and detritus along the river were clustered with exuviae, all apparently of Gomphus vastus. Several thousand individuals must have emerged from that general area of the river. As an example of the density, 230 cast skins were counted along one 20-foot stretch of the river bank. Some individuals had transformed directly on the sand banks and others at a height of seven feet.