AbstractIn 1981 and 1982, the following ant species and numbers were detected preying on pupae of the western spruce budworm, Choristoneura occidentalis Freeman, in eastern Oregon and western Montana: Formica obscuripes Forel, 174; Camponotus modoc Wheeler, 160; C. laevigatus Smith, 53; C. vicinus Mayr, 48; F. podzolica Francoeur, 43; F. accreta Francoeur, 32; F. neorufibarbis Emery, 12; F. lasioides Emery, 1; and Formica sp. (microgyna group). The Camponotus species and F. obscuripes were detected preying on budworm on one-third or more of the trees they foraged.