A heat budget for foraging honey bees (Apis mellifera L.) indicated that at 30–35°C all bees are in positive heat balance during flight. Observations of honey bees returning to their hives at high ambient temperatures support the conjecture that honey bees regulate head and thorax temperatures at high T_a by regurgitating droplets of honey stomach contents which are then evaporated. The proportion of returning bees with a droplet on the tongue increased with increasing shade temperature (T_s), from essentially no bees at 20°C to 40% of returning bees at 40°C. Pollen foragers carry relatively little fluid during the hottest periods, and pollen foraging decreased at high ambient temperatures. Thoracic temperatures of pollen collectors are significantly higher than thoracic temperatures of water and nectar gatherers at 40°C (46.13 vs 44°C). Additionally, water and nectar foragers with extruded droplets have slightly cooler heads and thoraces (38.94 and 43.22°C) than bees not extruding droplets (40.28 and 44.18°C). Wingloading and thoracic temperatures of bees are inversely correlated at high ambient temperatures (35°C) and this is probably caused by a higher propensity of heavier bees to extrude fluid, thus reducing thoracic temperature.

Animals avoid temperatures that constrain foraging by restricting activity to specific times of the day or year. However, because temperature alters the availability of food resources, it is difficult to separate temperature-dependent effects on foraging and the occupation of temporal niches. By studying two congeneric, sympatric Myrmecia ants we isolated the effect of temperature and investigated whether temperature affects foraging schedules and causes the two ants to be active at distinct times of the day or year. We monitored foraging activity and identified the ants' temperature tolerance in the laboratory by determining (1) critical thermal minima and maxima (CT_min and CT_max) and (2) the relationship between walking speed and temperature. Ants of Myrmecia croslandi were diurnal throughout the year, but ceased above-ground activity during winter. Surface temperature at the onset of foraging was 9.8–30.1°C, while their laboratory CT_min and CT_max were 10.4 and 48.5°C, respectively. Time of foraging onset was significantly influenced by surface temperature at time of sunrise and of onset. Ants of Myrmecia pyriformis were nocturnal throughout the year. Surface temperature at the onset of foraging was 5.4–26.2°C, while their laboratory CT_min and CT_max were 8.2 and 41.6°C, respectively. Time of foraging onset was not influenced by surface temperature, but solely by sunset time. We conclude that temperature determines the timing of foraging as well as the daily and seasonal foraging activity in M. croslandi, but has less obvious effects on M. pyriformis. In both species, CT_max was greater than temperatures at the natural foraging times.