There are three species of carpenter bees in Arizona (genus Xylocopa). The females are stout black bees, about one inch long, while the males can be black or golden depending on species. These are the largest native bees in the United States.
The female carpenter bee has a shiny, hairless, black abdomen. Its legs have dense, electrostatically charged hairs for gathering pollen.
Because of its large size, the carpenter bee often cannot fit into smaller flowers to get nectar. In that case, the bee makes an incision at the base of the flower to sip nectar. For larger flowers, such as cactus flowers, the carpenter bee is a valuable pollinator.
After mating, the female prepares for egg laying by using her strong mandibles to chew a half-inch diameter circular tunnel in a dead branch, soft lumber, or yucca or agave stalks. The hole can be up to 10 inches long. She stocks the cavity with nectar and pollen, then deposits an egg in the cavity. The egg chamber is partitioned off from the rest of the cavity with a wall made of saliva and wood debris thereby making separate brood chambers for each egg. She then repeats the process until the hole is filled with eggs. After five to seven weeks, young bees burrow out of the tunnel.
Carpenter bees often reuse their tunnels. Sometimes a single entrance hole will lead to many “galleries” that are used by several females.
According to the US Forest Service: “Carpenter bees are long lived, up to three years and there can be one or two generations per year. Often newly hatched daughters, live together in their nest with their mother. Biologists using observation nests or X-ray imaging techniques have observed returning foragers feeding other nest mates. These observations have led some entomologists to consider carpenter bees primitively social. However, unlike honey bees and bumble bees there are no queen or worker castes, only individual males and females.”
According to DesertUSA:
“In the spring, especially around nesting sites, the male carpenter bee may turn into a perfect showoff, careening and buzzing through the air and bumping clumsily into whatever gets in his way. He wants you to think that he’s aggressive and threatening—a bully. But he’s bluffing. He has no stinger. The female, as you might expect, behaves with far more dignity and restraint. She wants you to think that she’s a lady. But if you intrude into her space, she may attack. She will not be bluffing. She does have a stinger. She can inflict a painful wound.”
The US Forest Service notes that the “showoff” behavior of male bees is part of the mating ritual: “A widespread western US species, Xylocopa varipuncta, has an unusual mating system. Its green-eyed golden males have huge perfume glands in their thoraces. Territorial males take up positions in non-flowering plants near other males. As a group they actively release their rose-scented blend of chemicals. Females are attracted from downwind and choose a male with which to mate.”
DesertUSA goes on to note: “The damage done by carpenter bees to residence in a wooden structure is usually quite superficial. However, given enough time and enough seasons spent in the nest, the Carpenter Bee can chew a simple, but prolific tunnel & gallery network through a house’s timbers. Therefore, it is important to exterminate carpenter bees that have infested your home.”
The carpenter bee seems to be one of the primary native bees that pollinate agricultural crops.
For more general information about bees, see my article: Desert Bees