THE STUDY OF WILD BEES P . A . RACEY
Introduction MOST laymen often take the term wild bees to mean escaped colonies of the domesticated honeybee Apis mellifera. In fact, instances of successful escapes are rare, and such colonies seldom survive the winter. Not so rare, however, are the true wild bees, which in this country comprise 239 species of 26 genera. The most familiar are the Bumblebees, but also included are the Mining Bees, which burrow into the ground, the Mason Bees which construct nests of clay, and the Leaf-cutters, whose favourite nesting material is the garden rose. Considering the interest that has been focused on the truly social Honeybees and Bumblebees, it is surprising that so little is known about the rest of our native Apidae, especially since they raise some of the most stimulating and tantalising questions in entomology. In addition, they are important pollinators, a fact which has been exploited with great effect in North America. As well as discussing the biology of selected examples, I shall in this article be making an attempt to illustrate some of the evolutionary pathways that have led to more complex insect societies. PROSOPIS—the Bramble Bee The members of the primitive genus Prosopis build their nests in bramble stems or use the bore Channels made by other insects in old wood, banks of clay, vacated Lipara galls in reeds, and similar cavities. After mating, the small black female Prosopis begins the work of improving her tunnel by smearing the walls with a hardening slime, which resembles a very thin layer of cellophane. This is spread by the tongue, but whether it originates from glands in the head or from the Malpighian tubules of the alimentary canal is not known. It has been observed, however, that the bee continually bends its head ventrally towards the tip of its abdomen before a thread of slime is laid down. Functionally it is presumed that the slime makes the tunnels waterproof and proof also against leakage of the mixture of nectar and pollen which the female deposits there. Prosopis is only sparsely clothed with hairs, and does not appear to collect pollen on its body. It reveals its primitive lineage in the structure of its crop; whereas many bees have filtration devices to separate the pollen and nectar, Prosopis lacks this elaboration. Instead, the pollen and nectar must be swallowed together and regurgitated in the form of a thin gruel. As soon as a cell is stocked, an egg is laid in it and it is sealed with slime. A series of such cells are constructed along the length of the Channel.