Evolutionary Trends in the Subsocial Sawflies Belonging to the Neodiprion abietis Complex (Hymenoptera: Tenthredinoidea)

Populations of the Neodiprion abietis complex occur on firsand spruces in North America. A distinct western populationon white fir differs greatly in appearance from the four easternstrains, of which two feed on balsam fir and one each on blackand white spruce respectively. Differences in developmentalrates, larval survival on the various food plants, and hostselection by the females supply the isolating mechanisms betweenthe strains in the field. All populations cross-mated freelyin the laboratory, and the resulting hybrids indicate the transmissionof Several morphological and physiological characters. It isspeculated that the ancestral line of the complex fed on pinebefore a jump to spruce and then to balsam was made.