Temperature-dependent development and survival of immature stages of the alfalfa leafcutter bee, Megachile rotundata (Hymenoptera: Megachilidae)

Abstract

Stage-specific survival of immatures was greatest at 20-30°C (>75%). High temperatures of 32 and 35°C caused no greater mortality compared with that of 23-28°C. When estimates of survival were combined over all stages (egg to prepupal formation) high mortality of 98.6 and 73.3% was calculated for low constant temperatures of 15 and 18°C. At all other temperatures, combined survival for immature stages was >70%. Completion of development was observed at all constant temperatures for the egg and 4 instar stages. Rate of development increased with increased temperature from 15-35°C for the egg and first instar stages whereas for second, third and fourth instars, rate of development generally increased from 15-30°C and then decreased from 32-35°C. Frequency distributions of development times were constructed for each larval stage. Linear regression of development rate vs temperature provided an average base temperature of 15°C and 116 degree-days to complete immature stage development. -from Authors