Honeybee nestmate recognition: the thermal behaviour of guards and their examinees.

In honeybee colonies, guards protect their nest from various robbers including bees from other colonies. Infrared thermography showed that the guards and the bees examined by them (examinees) differ considerably in their thermal behaviour according to their particular role in the nestmate recognition process. The thorax surface temperature was on average higher and more variable in the examinees (36.1 degrees C, S.D.=4.14, N=1545, 303 bees) than in the guards (34.0 degrees C, S.D.=2.00, N=1681, 772 bees). During thorough examinations lasting longer than 30 s, more than 60 % of the examinees showed phases of intense thoracic heating of more than 2 degrees C (maximum temperature 48.5 degrees C), whereas most guards cooled down. Our data suggest that these examinees heat up their surface to enhance chemical signalling during examinations.