Egg.—Length .06 inch by .02 in width. In shape elliptical, rather narrow. Color dingy yellow, somewhat pulverulent. There were 56 of these found on the under side of a leaf, set on one end and about .05 inch apart. They were found September 9, 1883, at which time they were hatching, hence the length of the egg period is not known.

Young Larve.—Length .06 inch. Color dull yellow, more or less brownish at the ends, the sides of the head distinctly brownish. Each joint bears six branching spines concolorous with the body. In outline somewhat elliptical, the head being nearly as broad as the middle of the body, but the anal joint is not. Length of this period 5 days.

This singularly interesting larva occurs in abundance in the rapids of the Niagara above the Falls. The writer has taken it in other rapid streams in Western New York, also at different places in Michigan; besides, its occurrence in widely separated localities has been recorded by observers, hence we are led to believe that it is distributed throughout Eastern North America. Dr. Leconte has described another species, Ps. haldemanni, from the peninsula of California; its larva, it seems, has not been described.

The first notice of our larva is that by Dr. Kay in Part VI. (Crustacea), page 53, Zoology of New York, 1844. It is described in that work as a new genus and species of Crustacea, under the name Fluvicola Herricki; a poor figure is given.