The front wing has small stigma. When closed, the bee's short mandibles conceal the labrum. The clypeus is flat. Males of many species have much larger eyes than the females, which relates to their mating behavior. In the United States, two eastern species, "Xylocopa virginica" and "X. micans", occur. Three more species are primarily western in distribution, "X. sonorina", "X. tabaniformis orpifex", and "X. californica". virginica" is by far the more widely distributed species. In several species, the females live alongside their own daughters or sisters, creating a small social group. They use wood bits to form partitions between the cells in the nest. A few species bore holes in wood dwellings. Since the tunnels are near the surface, structural damage is generally minor or superficial. However, carpenter bee nests are attractive to woodpeckers, which may do further damage by drilling into the wood to feed on the bees or larvae. Carpenter bees have short mouthparts and are important pollinators on some open-faced or shallow flowers; for some they even are obligate pollinators, for example the maypop ("Passiflora incarnata") and "Orphium", which are not pollinated by any other insects. They also are important pollinators of flowers with various forms of lids, such as "Salvia" species and some members of the Fabaceae. However many carpenter bees "rob" nectar by slitting the sides of flowers with deep corollae. "Xylocopa virginica" is one example of a species with such nectar robbing behavior. With their short labia the bees cannot reach the nectar without piercing the long-tubed flowers; they miss contact with the anthers and perform no pollination. In some plants, this reduces fruit and seed production, while others have developed defence mechanisms against nectar robbing. When foraging for pollen from some species with tubular flowers however, the same species of carpenter bees still achieve pollination, if the anthers and stigmata are exposed together. Many Old World carpenter bees have a special pouch-like structure on the inside of their first metasomal tergite called the acarinarium where certain mites ("Dinogamasus" species) reside as commensals. The exact nature of the relationship is not fully understood, though in other bees that carry mites, they are beneficial, feeding either on fungi in the nest, or on other harmful mites.