On the morning of November 8th I was fortunate enough to watch the pupation of a caterpillar of Euvanessa antiopa, L. The operation has often been described, but it seems worth while putting another observation on record, which was carefully watched by Mr. Arthur Gibson and myself, from the time the larval skin first burst unitl the cremaster wad firmly fixed in the silk. The chrysalis first appeared through the black skin as a white dash in the middle of the second thoracic segment.