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Los Angeles County West Vector & Vector-Borne Disease Control District
Carpenter Bee
Carpenter
bees (members of the genus Xylocopa) are the largest bees found in
California. The larger species often approach an inch in
length. They are solitary bees that can be blue, black or tan and resemble
bumble bees. The females do have the capability of stinging
but are generally not aggressive if left undisturbed. As with other
bees, the males cannot sting. Carpenter bees get their
name because of their ability to tunnel through wood. They do not eat the
wood but construct long burrows in which to nest.
The Valley Carpenter Bee (X. varipuncta) is a commonly
seen member of this genus in Los Angeles County. They are most active
during the spring and summer. The females of this species are a metallic black
while the males are a pale yellowish brown (SEE PHOTOS ABOVE). They are
often seen burrowing into dead wood such as telephone poles, fence posts,
structural timbers and firewood. The entrance hole is circular and
approximately half an inch in diameter (SEE PHOTO OF STUMP BELOW). 
Carpenter bees are generally solitary and do not have a social
structure like that of the honeybee, but may often nest adjacent to each other in
the same piece of wood. Sometimes they may even share a single entrance
which leads to several separate burrows. Inside the burrow a female
creates a series of cells in which a ball made of nectar and pollen is
placed. One egg is laid on each ball before that cell is sealed as a
provision for the developing larvae.
Carpenter bees are beneficial insects that pollinate a
variety of trees and flowers. Homeowners are often concerned about these
bees due to their large size as well as the noise they make during flight and
excavation of their burrows. Although they are usually docile, they can sting if
disturbed as well as create damage to property if they are allowed to increase
the number of burrows in a structure over time. A homeowner can help
reduce the chance of carpenter bee damage by keeping exposed wood surfaces
painted and/or by using treated lumber.
(Photos on this page, H. Teodoro 2001)