The nest of the Brazilian stingless bee Melipona quinquefasciata

The neotropical genus Melipona, found from Mexico to Argentina, con- tains about 40 species. Most species live in woodland, some in savan- nahs. Nesting sites are found inside cavities within the trunk and branches of trees. M. quinquefasciata is exceptional in that it lives under- ground, where it occupies abandoned nest cavities dug by other ani- mals. We describe details of the nest and discuss the impact of the secluded nesting site for the physical conditions inside the nest. The stingless bee genus Melipona is neotropical and comprises about 40 species (Michener 2000), 36 of which are found in Brazil (Silveira et al. 2002). These species typically nest in cavities in the trunk or branches of living trees. Within the nest, a brood area and a storage area can be distinguished. Brood cells, arranged in horizontal combs, are within an involucrum which, in most species, is multilayered. Outside this involucrum are aggregated food pots of extraordi- nary size. Some contain honey, while others harbour pollen. From within the cavity a long and narrow tube leads to the single one-bee-wide nest entrance on the outside of the tree. We assume that within a cavity of a tall living tree the temperature is fairly constant, due to the water flow through the xylem, from the roots towards the leaves. The cavity, therefore, is a kind of incubator, where apart from a stabilised temperature the relative humidity will be constant and high. When such a cav- ity is selected as a nesting site, the bees cover its inner side-wall with a resin-like layer and separate the nest space from additional space in the cavity by heavy batumen plates. Such constructions suggest that the physical conditions inside the nest are well isolated from thermal and humidity fluctuations in the outside world. This interpretation finds additional support in the long and narrow inter- nal entrance tube, which precludes air streams, and only allows a slow gas exchange to occur by way of diffusion.