Effect of food quality, distance and height on thoracic temperature in the stingless bee Melipona panamica.

Stingless bees (Apidae, Meliponini) can recruit nestmates to good food sources. We present the first data showing that recruiting meliponine foragers at feeders and inside nests regulate their thoracic temperature according to net food profitability. Using infrared thermography, we found that Melipona panamica foragers elevated their thoracic temperature at profitable food sources (higher sucrose concentration, closer to the nest). At food sources, there is an increase of approximately 0.9 degrees C in thoracic temperature (Tth) per 1 mol l(-1) increase in sucrose concentration (at 20 m distance from nest: 1 mol l(-1) sucrose concentration, Tth=36.6+/-0.8 degrees C, T(a)=31.3+/-0.5 degrees C; 2.5 mol l(-1) sucrose concentration, Tth=36.9+/-0.6 degrees C, Ta=29.9+/-0.2 degrees C). Inside the nest, the difference between thoracic temperature Tth and ambient air temperature Ta (DeltaTnest) decreases by 0.4 degrees C with each 100 m increase in feeder-to-nest distance and increases by 0.1 degrees C per 1 mol l(-1) increase in sucrose concentration. The Tth of returning foragers was significantly higher at all tested sucrose concentrations (1.0-2.5 mol l(-1) sucrose concentration) and distances (25-437 m) as compared to Ta (at 2.5 mol l(-1) sucrose concentration: 25 m distance from nest, intranidal Tth=30.2+/-1.3 degrees C, Ta=24.8+/-0.7 degrees C; 437 m distance from nest, intranidal Tth=28.6+/-1.7 degrees C, Tnest=25.4+/-1.4 degrees C). For highly profitable food sources (2.5 mol l(-1) sucrose concentration and < or =100 m from the nest), forager Tth was slightly higher than that of randomly chosen control bees inside the nest.