About ten years ago, in sifting swamp mosses for Coleoptera, I met with certain active little insects which, despite their wingless form and almost microscopic size, were recognized as members of the order Hymenoptera. Some of the individuals so captured were afterwards described by Ashmead, in his Monograph of North American Proctotrypidæ, as Bœus minutus and B. piceus. Subsequently, B. americanus, Howard, and B. niger, Ashmead, were also discovered at Ottawa. My solitary example of the former species was found sluggishly crawling on the under surface of a stone in the chilly temperature of early spring, and one example of B. niger was taken with a sweeping-net at the end of September. With these two exceptions, all my specimens of the genus were taken from moss collected at the beginning of winter. All were females, as might be expected, for it is the females oniy of bees and wasps, and probably of all hymenoptera hibernating in the imago condition, that survive the winter in these northern lands.