In the beginning of July last I discovered in a bed of Typha latifolia, in the neighborhood of Montreal, a large number of the larvæ of Arzama obliquata. I have visited the spot repeatedly, and have had the larvæ under daily observation. One remarkable circumstance concerning them is that they are liable to attacks from the maggots of a fly belonging to the Ortalidæ, viz.:—The Cheœtopsis œnea of Wiedman, the Ortalis trifasciata of Say.