Abstract
Parasites of the sawflies Neodiprion abbotii (Leach), N. abietis (Harr.), N. lecontei (Fitch), N. nanulus nanulus Schedl, N. pinetum (Nort.), N. pratti banksianae Roh., N. swainei Midd., and the N. virginiana Roh. complex are separated by using characters of the parasite remains in the host cocoons from which the parasites emerged. Characteristics of the cast skin of the last larval instar of 11 species are described and illustrated in this paper; the remaining 29 species were described and illustrated in earlier papers (Finlayson, 1960a, 1960b, 1962). Keys are given to separate the species of the genera Exenterus and Lamachus that attack the above hosts, using characters of the cast skin of the last larval instar.