NEST TEMPERATURES AND THERMAL PREFERENCES OF A FOREST ANT SPECIES - IS SEASONAL POLYDOMY A THERMOREGULATORY MECHANISM

We measured nest temperatures and performed laboratory and field exper iments that determined thermal preferences of the forest ant Myrmica p unctiventris Roger. We tested the hypothesis that the seasonal cycle o f colony splitting (polydomy) that this species undergoes allows it to warm the brood, enhancing reproductive output. This ant species nests in performed cavities such as sticks, acorns, and hickory nuts. Labor atory choice experiments indicated that ants preferred to nest at a te mperature between 16 degrees C and 21 degrees C. Workers and brood had very similar temperature preferences; queens had slightly higher temp erature preferences. Field measurements of nest temperatures in Vermon t recorded an average summer daytime nest temperature of 22.6 +/- 0.38 degrees C s.e., n = 53 nests, with few differences between temperatur es in different types of nesting materials. Field experiments demonstr ated that ants colonized artificial nest sites on cooler plots prefere ntially to those on warmer plots (artificial nest sites on these plots differed by 1 degrees C in temperature, on average). Our results indi cate that M. punctiventris preferred to nest at temperatures at the co oler end of the spectrum of available nest sites in the field. Thus, o ur results lend no support to the hypothesis that seasonal polydomy is a thermoregulatory mechanism that these ants employ to place their br ood in the warmest available nest sites.