THERMODYNAMICS IN NESTS OF TWO MELIPONA SPECIES IN BRASIL

SUMMARY Thermodynamics within 10 nests of Melipona rufiventris and M. seminigra were recorded during 48 horurs with thermocouple probes. Strikingly similar patterns were found for both species. Homeostasis did not occur; temperatures within the brood area, honey and pollen stored in pots and nest cavity space all followed ambient temperature fluctuations. Nest temperatures were consistently higher than ambient in all portions of the nest except the upper extremith of vertically elongate hives. Near the brood, temperature fluctuations were damped and displayed a time lag of one to two hours in following ambient temperature. The thoracic temperature of resting worker bees was near 34°C, and the average brood temperature was 31 — 32°. The involucrum surrounding the brood retained a portion of radiated heat from immatures and workers resting between combs, and brood temperature was two to three degrees higher than internal nest temperature immediately outside the involucrum. The brood chamber, the largest nest structure, contained from 2000 to 6000 immatures, and adult bee populations were less than 1000. The brood nest acts as a heat source at the base of the nest and dissipates heat upwards, creating a thermal gradient. Immature bees appear to supply most of the heat for the nest, and excess heat is shunted by fanning workers through the nest entrance, usually connected to the brood area. There is no evidence of evaporative cooling from water brought into the nest in these or other species of Meliponinae.