Microclimate and season affect flight initiation in the alfalfa leafcutting bee

Weather conditions are often reported for a large area, but small-bodied organisms experience abiotic conditions on a finer scale. For insects that nest in cavities, the temperatures in and around the cavity may be important for flight initiation. Cavities can expose nesting bees to conditions that differ from broad weather readings and may affect when or if bees fly. The purpose of this study is to determine which environmental factors influence flight in early and late summer and how altering internal cavity temperatures contributes to flight initiation in a cavity-nesting bee, Megachile rotundata. Two types of nest boxes were created to monitor flight initiation. The first nest box had no manipulations and recorded several abiotic environmental conditions, including multiple temperatures, light, wind speed, and humidity. The second nest box had one side heated and the other unmanipulated. The first flight for individual bees was recorded and measured from 7-11 am daily. All environmental variables at the time of first flight were significantly different between the early and late seasons except for air pressure. Throughout the summer, temperatures inside and at the face of the first nest box design were higher than ambient at first flight. Heating the nest cavities promoted flight at lower ambient temperatures and at earlier times. Understanding how abiotic conditions affect flight initiation will help model flight behavior in response to climate change and allow farmers to provide optimal flight conditions when weather is unfavorable.