The final instar larva is described from specimens collected near Petersham, Massachusetts; Havelock, Ontario; and Masham, Quebec. It closely resembles the larva of W. lintneri, the only other member of the genus, but can be distinguished from it by the shorter length of the lateral spines on abdominal segment 9; these spines are about 1/5 the length of the segment including the spine, but 1/4 the length or longer in lintneri. W. fletcheri shares with W. lintneri the combined presence of dorsal hooks on abdominal segments 3 through 9 and lateral spines on segment 9 only, characters that are unique among North American corduliid genera. The larval habitat is described and observations of adult behavior and species associations are reported.