Everyone who travels the forests or roads of Ontario and the provinces east of it must be familiar with the tent caterpillars of the genus Malacosoma. The best known of these is the orchard, eastern, or American tent caterpillar, Malacosoma americana Fab., which makes its large grey “tents” on chokecherry, apple, hawthorn, wild plum and other trees and shrubs, chiefly of the family Rosacea.