EFFECTS OF TEMPERATURE ON DEVELOPMENTAL RATE OF THE IMMATURE STAGES OF THE ALFALFA WEEVIL, HYPERA POSTICA (COLEOPTERA: CURCULIONIDAE)

Abstract

When Hypera postica (Gyll.) was held at 11 constant temperatures, the hatching rate for eggs increased with rise in temperature from 8° to 20 °C and remained maximal to 32 °C. None hatched at 6 °C. Larvae survived at 10° to 35 °C with high mortality only at these limits. Pupae survived at all temperatures above 10 °C but at 35 °C half of the adults were deformed. Duration of all stages decreased with rise in temperature up to 32 °C. Developmental rates plotted against temperature did not deviate significantly from fitted curves of the form 1/y = K/(1 + e^a−bx).The optimum temperature, based on maximal rates of development and survival, for eggs and young larvae was near 32 °C and for older larvae and pupae, 30 °C. Accumulated degree-days above a base of 10 °C during development of H. postica at two Ontario locations did not differ significantly from thermal requirements calculated.