Species of the genus Xylocopa comprising tribe Xylocopini of the subfamily Xylocopinae are referred as large carpenter bees (as opposed to small carpenter bees in genus Ceratina) due to their nesting behavior. Most species burrow into plant material such as dead wood or bamboo but species in genus Proxylocopa are ground nesters. Xylocopini are large, robust bees, 13 to 30 mm long, and some of the principal characters of the tribe are probably associated with large size. Among these are the loss of the stigma, the very long prestigma and marginal cell, and the strongly papillate distal parts of the wings. Another distinctive feature is the long first flagellar segment, longer than the second and third taken together; this character occurs in various unrelated large bees and may be somehow related to large size or fast flight. The rather short proboscis is distinctive, the parts being strongly sclerotized, the postpalpal part of the galea blade like and presumably used to cut into the corollas of tubular flowers to rob the nectar. The Xylocopini typically have three submarginal cells, but the first and second are sometimes partly or wholly fused owing to the disappearance of the posterior part or the whole of the first submarginal crossvein. Unlike other Xylocopinae, the bees of the tribe have no arolia, although the densely hairy planta projects somewhat between the claws (Michener, 2007). Male carpenter bees often have holotypic eyes (meeting on the top of the head) associated with territorial behavior. They perch on vegetation and fly up to intercept rivals and potential mates. This behavior may be perceived as aggressive, but like all male bees territorial Xylocopa cannot sting. The stings of females are used solely for defense of their nests, so these important pollinators pose little danger to humans. Large carpenter bees are unusually long-lived among bees and so young bees may emerge while their mother is still active and share a nest with her, contributing to its defense (a form of subsociality).