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Phylum Arthropoda

Class Insecta

Order Hymenoptera

Family Apidae

Subfamily Xylocopinae

Tribe Xylocopini





The subfamily Xylocopinae (family Apidae) occurs worldwide, and includes the large carpenter bees (tribe Xylocopini), the small carpenter bees (tribe Ceratinini), the allodapine bees (tribe Allodapini), and the relictual genus Manuelia (tribe Manueliini). The Xylocopini comprise a single genus, Xylocopa, and occur on all continents except Antarctica. The Ceratinini also comprise a single genus, Ceratina, also with a worldwide distribution, but the Manueliini comprise only three species which are restricted to Chile and the Lakes Region in Argentina. The allodapines are restricted to sub-Saharan Africa, Madagascar, Southeast Asia, and Australasia, with a rare genus Exoneuridia also occurring in montane regions of the Middle East.

The vast majority of the Xylocopinae species make nests in dead wood, stems, or pith, and while many are solitary, many are also communal or primitively social, and some genera of allodapines commonly form eusocial colonies. Xylocopinae have a cavity between the thorax and abdomen, which provides accommodation for a colony of predatory mites, cleaning their hosts of external parasites.

Carpenter bees (the genus Xylocopa in the subfamily Xylocopinae) are large bees distributed worldwide. Some 500 species of carpenter bees are in the 31 subgenera. Their common name is because nearly all species build their nests in burrows in dead wood, bamboo, or structural timbers (except those in the subgenus Proxylocopa, which nest in the ground). Members of the related tribe Ceratinini are sometimes referred to as "small carpenter bees".

Carpenter bees are large, sturdy, shiny, black-coloured bees, some species having yellow markings on their heads. Carpenter bees may be mistaken for bumblebees.

The marginal cell in the front wing is thin and stretched and the apex bends away from the costa. The front wing has small stigmata. The bee's labrum is concealed by the short mandibles when closed. The clypeus is flat. The thoracic menanotum is presented upright and is part of the rear surface and is almost perpendicular to the dorsal surface. The basitarsi are of the same length as the associated tibiae, and the hind pair of basitarsi is hirsute.

Carpenter bees are traditionally considered solitary bees, though some species have simple social nests in which mothers and daughters may cohabit. Examples of this type of social nesting can be seen in the species Xylocopa sulcatipes and Xylocopa nasalis. When females cohabit, a division of labor between them occurs sometimes. In this type of nesting, multiple females either share in the foraging and nest laying, or one female does all the foraging and nest laying, while the other females guard.

Solitary species differ from social species. Solitary bees tend to be gregarious and often several nests of solitary bees are near each other. In solitary nesting, the founding bee forages, builds cells, lays the eggs, and guards. Normally only one generation of bees live in the nest. Xylocopa pubescens is one carpenter bee species that can have both social and solitary nests.

Carpenter bees make nests by tunneling into wood, vibrating their bodies as they rasp their mandibles against the wood, each nest having a single entrance which may have many adjacent tunnels. The entrance is often a perfectly circular hole measuring about 16 mm (0.63 in) on the underside of a beam, bench, or tree limb. Carpenter bees do not eat wood. They discard the bits of wood, or reuse particles to build partitions between cells. The tunnel functions as a nursery for brood and storage for the pollen/nectar upon which the brood subsists. The provision masses of some species are among the most complex in shape of any group of bees; whereas most bees fill their brood cells with a soupy mass, and others form simple spheroidal pollen masses, Xylocopa species form elongated and carefully sculpted masses that have several projections which keep the bulk of the mass from coming into contact with the cell walls, sometimes resembling an irregular caltrop. The eggs are very large relative to the size of the female, and are some of the largest eggs among all insects.

Two very different mating systems appear to be common in carpenter bees, and often this can be determined simply by examining specimens of the males of any given species. Species in which the males have large eyes are characterized by a mating system where the males either search for females by patrolling, or by hovering and waiting for passing females, which they then pursue. In the other mating system, the males often have very small heads, but a large, hypertrophied glandular reservoir is in the mesosoma, which releases pheromones into the airstream behind the male while it flies or hovers. The pheromone advertises the presence of the male to females.