East Texas Ips species contained 4 specific internal nematodes; I. avulsus (Eichhoff) were infected with Parasitylenchus avulsi Massey, I. grandicollis (Eichhoff) with Contortylenchus grandicolli (Massey) Rlihm, and I. calligraphus (Germar) with Contortylenchus elongatus (Massey) Nickle and Parasitaphelenchus sp. In all 3 bark beetles, infection peaked in July and August when 50-58% of adults from naturally attacked pine trees contained nematodes. Infection levels declined to 20-30% during January and February. Infected I. grandicollis and I. avulsus adults appeared lighter in color than noninfected adults. Nematode infection apparently delayed emergence of both sexes of I. grandicollis and females of I. avulsus. In I. grandicollis, nematode infection did not affect ability to construct egg galleries or number of offspring produced. Supercooling temperatures for infected I. grandicollis and I. calligraphus were no different than those of noninfected beetles.
Coster, Jack E. and Hoffard, William, "Endoparasitic Nematodes of Ips Bark Beetles in Eastern Texas" (1976). Faculty Publications. 334.