Colony Defense Strategies of the Honeybees in Thailand

The colony defense strategies of the three honeybee species in Thailand were studied to examine the influence of predation on tropical honeybee societies. Each species focuses its defenses upon different stages in the predation sequence of detection—approach—consumption. This radiation in defense strategies apparently reflects each species' preadaptation by worker size (small, medium—sized, or large) and nest site (cavity or tree branch) to a different pattern of colony defense. Wasps, birds, and primates probably have difficulty finding the small, dispersed colonies of Apis florea, whose nests are built low on the branches of dense, shrubby vegetation. Once found, however, they are easily approached and overpowered because their low, exposed nests are accessible and their small workers inflict relatively painless stings. When overwhelmed, the bees quickly abandon their nest; later, they return to salvage wax. Ants find A. florea nests easily and at least one species (Oecophylla smaragdina) easily kills these small bees. However, sticky bands of resin encircling the nests' slender substrate branches prevent ants from invading A. florea nests. Cavity—nesting colonies of Apis cerana are conspicuous with their medium—sized bees streaming in and out of low, clearly visible entrance holes in caves and hollow tress. However, gaining access to A. cerana nests is difficult. Large predators cannot pass through the small entrance opening and small predators are overpowered by entrance guards. But if a large predator can breach a nest cavity's walls, it faces an only moderately powerful stinging defense. Apis cerana colonies are relatively small and their workers are not fiercely aggressive. Predators easily find the large, sometimes aggregated colonies of Apis dorsata, whose nests hang in the crowns of the tallest forest trees. But only skilled fliers and climbers can reach these lofty nests. Those which do face massive stinging attacks from the large colonies of these relatively giant, ferocious bees. Nests of both open—nesting species, Apis florea and A. dorsata, are protected by a three— to six—layer curtain of bees over the comb. Apis cerana colonies lack these curtains but are protected by their nest cavity walls. A curtain of inactive guards requires a large labor force. The high worker: brood ratio in A. florea relative to A. cerana colonies suggests that the age polyethism schedules of the open— and cavity—nesting species are tuned differently to generate the appropriate proportions of guard bees. Each species' colony defense system consists of numerous interwoven lines of adaptation, including nest site, nest architecture, colony population, labor allocation to defense, age polyethism schedule, colony mobility, and worker morphology, physiology, and behavior. Predation has been a pervasive and powerful force in the evolution of these tropical bee societies.