THE ECOLOGICAL SIGNIFICANCE OF AN ARBOREAL NEST OF BOMBUS PULLATUS IN COSTA RICA

Abstract

A Bombus pullatus nest 5.5 m above the ground in the foliage of a banana plant was collected at 1,400 m elevation near San Vito de Java, Costa Rica. Containing 36 presumably virgin queens, 259 workers, and 48 males, the colony has certain traits suggesting perenniality or mobility. It is postulated that the failure of bumble-bees to attain an abundance in the wet lowland tropics equivalent to that in temperate mesic habitats may be due to a shortage in tropical habitats of dry underground cavities plus the ephemeral nature of arboreal nest sites, increased predation on both individual bees and entire nests, and increased competition for arboreal nest sites by smaller social bees and ants.