Nematode Parasites of the Douglas-Fir Beetle in Idaho and Utah

During 1958–62, 738 adult Douglas-fir beetles, Dendroctonus pseudotstlgae Hopkins, from Idaho and Utah were examined for nematodes. Ectoparasitic species found were primarily Mikoletzkya sp. but included some Ektaphelenchus obtusus Massey and Aphelenchoides sp. In order of their abundance, endoparasites were: Contortylenchus reversus (Thorne) Ruhm, Parasitaphelenchus sp. (both in the body cavity) and Parasitorhabditis obtusa (Fuchs) Dougherty (in the midgut). In 1965, Sphaerulariopsis dendroctoni (Massey) Nickle was found in the beetle for, the first time. About 93% of the beetles were infested with at least one species of nematode. Rates of parasitism varied little by sex of beetles; greater differences occurred between localities, between standing and felled trees, and with maturity of beetles.