LIFE-HISTORY OF IMMATURE MAIZE WEEVILS (COLEOPTERA, CURCULIONIDAE) ONCORN STORED AT CONSTANT TEMPERATURES AND RELATIVE HUMIDITIES IN THE LABORATORY

Life history of immature maize weevils, Sitophilus zeamais Motschulsky , was studied at 10-40 degrees C and 43-76% RH. The optimal quantity o f corn for minimizing density effects and the optimal observation freq uency for minimizing disturbance effects were determined at 30 degrees C and 75% RH. The quantity of corn (32-256 g) provided to five female s ovipositing for 24 h did not affect duration of development, but the number of progeny produced increased asymptotically as the quantity o f corn provided increased. Frequency of observation (from 1- to 14-d i ntervals) did not affect duration of development or number of progeny produced. Using moisture contents measured in the life history study, an equation was developed for predicting equilibrium moisture content of corn from temperature and relative humidity. Duration of immature d evelopment did not vary with sex, but did vary with test. This suggest s that insect strain or chemical composition of the corn must be inclu ded as factors in a model predicting effects of environment on duratio n of immature development. Survival from egg to adult emergence was gr eatest at 25 degrees C. Sex ratio of emerging adults did not differ fr om 1:1. The number of multiply-infested kernels was low at all environ mental conditions, and survival from egg to adult emergence in these k ernels averaged 18%. Maximum daily rate of fecundity, duration of deve lopment, and number of progeny produced were optimal at 30 degrees C a nd 75% RH. An index of environmental suitability indicated that 30 deg rees C and 75% RH was the optimal environment for growth of maize weev il populations on corn. Implications of the results for managing maize weevil populations are discussed.