Two sawfly species that feed on white fir were studied in Modoc County, California: Neodiprion near deleoni Ross and N. abietis complex. Neodiprion near deleoni comprised 91 percent of the field Neodiprion populations and spun opaque brown cocoons in the litter or soil. Neodiprion abietis accounted for 9 percent of the field population and spun translucent cocoons that appear green and are attached to foliage. Full-grown larvae, pupae, and adults of the two strains were morophologically distinct, though eggs and young larvae were not. Differences in morphology, phenology, physiology, and behavior are described for the two species.

Mortality factors are identified, primarily for N. near deleoni. Parasitoids emerged from eggs and cocoons; many parasitoids that emerge from cocoons attack larvae. Larval predation was observed only rarely, except for predation by theridiid spiders. Sampled cocoons showed: 16 to 21 percent parasitized, 21 to 22 percent attacked by predators, 24 to 37 percent unknown mortality, and 25 to 34 percent sawfly emerged. Encapsulated ichneumonid eggs were found in 10 to 41 percent of emerging sawflies.