The effects of temperature and humidity on eggs and of temperature on larvae of Artipus floridanus Horn, Pachnaeus litus Germar, Pachnaeus opalus (Olivier), and Pantomorus cervinus (Boheman) were determined. The low and high temperatures lethal to neonate larvae were determined by 12-hour exposure to temperatures ranging from -5 to 50@*C. The combined effects of temperature and RH on egg hatch were determined. Saturation vapor pressure deficit accounted for 59.4, 81.9, and 94.2% of the observed variation in percent egg hatch for A. floridanus, P. opalus, and P. cervinus, respectively. The thermal constant (K) and developmental threshold (@f) was calculated for egg development of each species. A. floridanus was reared on artificial media at constant temperatures from 15 to 35@*C. At 35@*C, larvae died at ecdysis to the last instar. Between 20 and 30@*C, 1412 degree days were required to complete development. Larvae held at 15@*C had not pupated after 8 months (3600 degree days).