Entomophthora crustosa n. sp. pathogenic for Malacosoma species (principally M. disstria Hbn.), is described. It is characterized in the conidial state by a hymenial coating which, at maturity, forms a crust-like covering, cinnamon brown, over the surface of infected insects, and by conidial size. In the resting spore (zygospore) state the distinguishing attributes are ornamentation of the zygospores and their mode of development. The pathogen grows readily on coagulated egg-yolk media.
The fungus is briefly compared with 10 other closely related Entomophthora species. Entomophthora crustosa seems to be of widespread occurrence in eastern North America.