Introduction
Bees of all kinds belong to the order of insects known as Hymenoptera, literally "membrane wings". This order, comprising some 100,000 species, also includes wasps, ants, ichneumons and sawflies. Of the 25,000 or more described species of bees, the majority are solitary bees most of which lay their eggs in tunnels, which they excavate themselves. In some species small numbers of females may share a single tunnel system, and in other cases there may be a semi/social organization involving a hierarchical order among the females, these bees provide a supply of food (honey and pollen) for the larvae, but there is no progressive feeding of the larvae by the adult bees. Honeybees belong to the family of social bees which includes bumble bees and the tropical stingless bees of the genus Meliponinae. The social bees nest in colonies headed by a single fertile female, the queen, which is generally the only egg layer in the colony. Foraging for nectar and other tasks such as feeding the queen and the larvae, cleaning brood cells and removing debris, are carried out by a caste of females, the Workers. Honey and pollen is stored, and larvae are reared in cells made from wax secreted by the worker bees. Typical colonies may amount to no more than a few dozen insects, and may be annual as in the case of bumble bee colonies, or they may number several tens of thousands and persist for a number of years, as in the case of honeybees and species of Meliponinae. The sub-family Apinae or honeybees, comprises a single genus, Apis, which is characterised by the building of vertical combs of hexagonal cells constructed bilaterally from a midrib, using only the wax secreted by the worker bees.
The cells are multifunctional, being used repeatedly for rearing the larvae and for the storage of honey and pollen. Progressive feeding of the larvae is carried out by young bees with food produced by glands in the head of the bee from honey and pollen. Two attributes of honeybees which have been essential to their evolution and biology are their clustering behaviour and, particularly in the case of the cavity-nesting species, their ability to cool the nest by evaporation of water collected outside. These attributes enable the colonies to achieve a marked degree of temperature regulation within the nest irrespective of the external temperature. The genus Apis was thus enabled to colonise a wide variety of environments, ranging from tropical to cool temperate. The Meliponinae which lack this capability are confined to tropical regions. Another behavioural character of honeybees is the communication of information about food sources and the recruitment of foragers by "dance language". The accurate dissemination of information concerning direction and distance of forage areas leads to efficient exploitation of food sources. Whereas representatives of most types of bee were indigenous to all the continents, bees belonging to the genus Apis were originally to be found only in the Old World, namely Asia, Africa and Europe. This suggests that the genus appeared much later than the other types. The genus comprises four species: Apis florea, the Little Honeybee; Apis dorsata, the Giant Honeybee; Apis cerana, the Eastern Honeybee; and Apis mellifera, the Western Honeybee. (Some authors include Apis laboriosa and Apis andreniformis as separate species, but it is likely that these are geographical subspecies of Apis dorsata and Apis florea respectively which show greater physical variations than the other subspecies and are possibly in a more advanced stage of speciation.