EFFECT OF FORAGING DISTANCE ON THE THERMAL-BEHAVIOR OF HONEYBEES DURING DANCING, WALKING AND TROPHALLAXIS

By means of infrared thermography and without disturbing social intera ctions, the correlation between thoracic temperature in honeybees, Api s mellifera carnica, upon their return to the hive and their foraging distance was investigated. Thoracic temperature while dancing and walk ing and during trophallactic contact with hive bees decreased with inc reasing flight distance. In bees foraging 0.5, 1, 1.5 and 2 molar sucr ose solutions from a distance of 120 m, dancing temperature amounted t o 38.4, 40.1, 40.9 and 40.6 degrees C, respectively; while in bees for aging from a distance of 2950 m it amounted to 36.6, 38.4, 38.6 and 39 .1 degrees C, respectively. The rate of decrease in dancing temperatur e per 1000 m increase in flight distance was 0.64, 0.47, 0.81 and 0.54 degrees C with a 0.5, 1, 1.5 and 2 molar sucrose solution, respective ly. Both at short and at long flight distances, the relationship betwe en thoracic temperature and sucrose concentration of the food followed a non-linear curve, which flattened at concentrations higher than 1 m ol/l. The experiments showed that inside the hive the foragers' level of thermoregulation depends not only on the energy (sugar) content of the food; but ether, the level of thermoregulation corresponds to the general quality of the food source, which includes both energy content and distance from the hive. Because the thermal behaviour of foragers correlates with several behavioural parameters indicating the bees' f oraging tendency and their eagerness to dance, thoracic temperature se ems to be a correlate of the profitability of foraging.