EFFECTS OF TEMPERATURE ON DEVELOPMENT OF THE IMMATURE STAGES OF THE CEREAL LEAF BEETLE, OULEMA MELANOPUS (COLEOPTERA: CHRYSOMELIDAE)

Abstract

Survival and development rates were obtained for the cereal leaf beetle, Oulema melanopus (L.), at 12 constant temperatures. Rates of survival for eggs were high at temperatures ranging from 12°C to 32°C, but none hatched at 6°C or 34°C. Larvae survived at 8° to 32°C with no drastic rise in mortality at the extremes; mortality at 34°C increased with larval age. Pupal survival was low at all temperatures from 8°C to 32°C, ranging from about 3% at these limits to 40% at intermediate temperatures (14° to 30°C). Duration of egg and larval stages decreased with rise in temperature up to 30°C, and that for pupae, 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 threshold for complete development was at some point between 6°C and 8°C. Thermal requirements, with 7°C as developmental zero, were calculated at 105, 41, 36, 43, 46, and 282°D, respectively, for the eggs, the four larval instars and the pupae. Accumulated heat units (°D₇) during development of O. melanopus in field plots at Ottawa did not differ significantly from those expected. Similar calculations using a base of 9°C (ca. 48°F) predicted development equally well.