TEMPERATURE-DEPENDENT DEVELOPMENT AND SURVIVAL OF IMMATURE STAGES OF THE ALFALFA LEAFCUTTER BEE, MEGACHILE-ROTUNDATA (HYMENOPTERA, MEGACHILIDAE)

Survival and development of eggs and larvae of the alfalfa leafcutter bee, Megachile rotundata, were determined for 9 constant temperature r anging from 15-35-degrees-C. Stage-specific survival of immatures was greatest at temperatures of 20-30-degrees-C (> 75%) and high temperatu res of 32 and 35-degrees-C caused no greater mortality compared with t hat of 23-28-degrees-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-degrees-C. At all other temperatures, combined survival for immature stages was high (> 70%). Completion of development was observed at all constant t emperatures for the egg and 4 instar stages. Rate of development incre ased with increased temperature from 15 to 35-degrees-C for the egg an d first instar stages whereas for second, third and fourth instars, ra te of development generally increased from 15 to 30-degrees-C and then decreased from 32 to 35-degrees-C. Frequency distributions of develop ment times were constructed for each larval stage. A Weibull function provided a good fit to a single, temperature-independent distribution of normalized development times. Linear regression of development rate versus temperature provided an average base temperature of 15-degrees -C and 116 degree-days to complete immature stage development.