This study presents calibrations allowing absolute ther- mographic temperature measurements in honey bees and hornets. The band emissivity ( 3.5-5.6 m) of a heated honey bee thorax (mesosoma) is limited to a range of 0.955-0.990. The development of thoracic heat production was in- vestigated in young honey be es (Apis mellifera carnica). Five-hour-old bees did not actively produce heat in their thoraces, whereas l- and 2-day-old bees did. We made continuous thermograpbic temperature re- cordings of adult honey bees during stops at a nearby feeding bowl containing 1- sucrose solution. At ambient M temperatures of 23.8-26.2C, thoracic surface tempera- tures were increased up to 45C, with mean values of 41.4C (41.1 43.7C) after landing and 43.5C before taking off. Similarly, hornets ( ) Vespa crabro actively regulated their body temperatures when fed with honey in front of their nest. Thoraces reached a mean minimum tempera- ture of 32.7C 37.4 36.8C before taking off (ambient and temperature 18 18.6C). Head ( 29.2C) and abdomen ( 25.2C) always remained cooler than the thorax.