The Life History of Stenopelmus rufinasus (Coleoptera: Curculionidae)

Abstract

The weevil Stenopelmus rufinasus Gyllenhal lives and feeds on the leaves of the aquatic fern Azolla . Eggs are laid individually in the tip of the shoot, and the first of the 3 larval instars mines the leaves for a short period before feeding externally. The mature larva uses an anal secretion to form a cocoon on the Azolla leaf. The life cycle was completed in approximately 18 days at a mean room temperature of 76.5°F, and in 11 days at a constant 90°F; mortality was heavy at the latter temperature. Mortality was also attributable to the fungus Beauveria bassiana in laboratory cultures. Since neither the larvae nor the adults remained submerged for long periods, the species should be considered semiaquatic. Four to 6 generations a year seem probable in California, with the adults as the overwintering stage.