Biology of Pityophthorus pulchellus tuberculatus (Coleoptera: Curculionidae: Scolytinae) in Lodgepole Pine in Northern Idaho

Abstract

The twig beetle, Pityophthorus pulchellus tuberculatus Eichhoff, infests dead branches of pines in western United States and Canada, including lodgepole pine, Pinus contorta Douglas, in northern Idaho. Adult broods overwintered in their host and emerged and colonized new hosts in late April. Males initiated galleries and were joined by up to seven females, each of which constructed an egg gallery radiating from a central chamber. Galleries had an average of 4.7 egg niches each with an egg that was large relative to the mother beetle. Two larval instars were recognized. Dentition of larval mandibles differed in shape from that in literature. Mature larvae pupated either in a cell excavated on the wood surface or in a cell below the wood surface. First-generation adults mined extensively in the inner bark and wood before emerging to infest new trees in late June. Their progeny became adults beginning in early August and likewise mined and fed on the inner bark and wood before overwintering. Predacious beetles present as larvae in the galleries included Enoclerus lecontei (Wolcott) (Coleoptera: Cleridae) and Lasconotus sp. (Coleoptera: Zopheridae). Parasitoid Hymenoptera reared from infested trees were Cosmophorus pityophthori Rohwer (Braconidae), Phasmidiasta n. sp. (Braconidae), Spathius sp. (Braconidae), Acerocephala n. sp. (Pteromalidae), Metacolus fasciatus Girault (Pteromalidae), Rhaphitelus maculatus Walker (Pteromalidae), Rhopalicus sp. (Pteromalidae), and an unidentified pteromalid.