The bark gnawing beetle, Nemosoma attenuatum Van Dyke (Coleoptera: Trogossitidae), has been previously described as an associate of twig beetles in the genus Pityophthorus Eichhoff (Coleoptera: Curculionidae) and other bark beetles. Presented here are post hoc observations on the seasonal occurrence of N. attenuatum, collected and identified as part of an ecological study of Pityophthorus species inhabiting native Monterey pines and their potential role as vectors of a fungal pathogen Fusarium circinatum. Adult N. attenuatum were recovered from flight traps between May 2001 and July 2003. Additionally, adult and larval N. attenuatum were discovered in cut P. radiata branches suspended in canopies of P. radiata in native stands. The highest flight trap counts were recorded during May 2001, suggesting a mass emergence. The highest numbers of N. attenuatum were observed from branches suspended between January to March. Two N. attenuatum larvae were discovered within the galleries of Pityophthorus setosus, although neither was observed feeding on any Pityophthorus spp. Neither eggs nor pupae were discovered during the course of this study. Also included are a literature review and the results of a museum survey of five major North American insect collections for Nemosoma species from North America.