A few years since I described a colony of Spanner caterpillars (Geometridœ) belonging to an undeterminded species, and the description appeared afterwards in this journal. These larvæ were remarkable for their mimicry, in color and shape and attitude, of dead leaves. There could be no question that they belonged to the category of protective appearance, to which so many green and brown tinted larvæ belong, which share these “cosmical color.s”