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INTRODUCTION.
Carpenter bees get their common name from their habit of boring into wood to make
galleries for the rearing of young. These are worldwide in distribution with 7 species
occurring in the United States.
RECOGNITION.
Adult body length about 1/2-1" (12.5-25 mm); robust in form, resembling bumble bees,
but with top surface of abdomen largely bare and shining. Hind tibiae with apical spurs.
Front wing 2nd submarginal cell triangular; hind wing with a small jugal lobe (lobe on
rear margin near body).
SIMILAR GROUPS.
Bumble bees (Apidas) have hairy abdomen with yellow markings, 2nd
submarginal cell somewhat rectangular to pentagonal, and hind wings lack a jugal lobe.
Some robber flies (Diptera: Asilidas) which resemble bumble bees,
with only I pair of wings.
Some hawk moths (Lepidoptera: Sphingidas) which resemble bumble bees,
with siphoning mouthparts.
REPRESENTATIVE SPECIES.
- The carpenter bee, X virginica (Linnaeus), is the most common eastern species and its
range extends westward to Kansas and Texas. It is about 1 " (25 mm) long and closely
resembles the bumble bee except that the abdomen is black and shiny instead of at least
partially covered with yellow hairs. The male has a yellow face, whereas, the female's is
black.
- The California carpenter bee, X. califomica Cresson, is found in the north Coast Ranges
and the Sierra Nevada of California and in Oregon's Cascade Mountains. This bee is 3/4-1
" (20-25 mm) long and both sexes can be mostly metallic green or blue with
grayish/dusky wings. The male's pronotum has orange, yellow, or white hairs and its lst
abdominal segment has whitish hairs.
- The valley carpenter bee, X. varipuncla Patton, is found primarily in the valleys and
lower foothills of California and Arizona. This species is about 3/4" (18-20 mm)
long. The female is shiny black with brilliant metallic purple, brassy, or bronzy
reflections, in stark contrast to the golden brown or buff color of the male. The female's
wings are somewhat smoky.
- The mountain carpenter bee, X. tabaniformis Smith, is found mostly in the foothills and
mountains of Arizona, California, Nevada, and Oregon. This bee is about 1/2-5/8"
(12-17 mm) long and both sexes are black. The male's head has yellow and white hairs mixed
with black hairs.
BIOLOGY.
Carpenter bees are not social insects and do not live in nests or colonies. The adults
overwinter, typically in abandoned nest tunnels. In the spring, the survivors emerge and
feed on nectar. Then mating begins and extends into nest-construction time. The mated
female may either reuse an old gallery, construct a new one by lengthening an old gallery,
bore an entirely new one, or extend a gallery from a common entrance hole. The female
typically bores a circular hole (same diameter as her body) straight into the wood across
the wood grain for a distance equal to her body length. Then the gallery takes a
right-angle turn, usually with the grain of the wood and parallel to the outer
longitudinal surfaces. New galleries average 4-6" (10-15 cm) long but galleries
developed/used by several bees may extend up to 1 0 feet (3 m).
The female provisions each gallery cell starting at the closed end of
the gallery with a mass of pollen and regurgitated nectar upon which she lays a single
egg. This portion of the gallery is then sealed off with a chewed wood-pulp plug, making a
chamber or cell. This process is repeated until a linear series of 5-6 cells is completed,
about 1 cell per day. Developmental time (egg to adult) for the carpenter bee (X.
virginica) is about 36 days and for the mountain carpenter bee (X. tabaniformis), it is
about 84-99 days.
HABITS.
Females of the carpenter bee (X. virginica) will nest in a wide range of woods, but prefer
weathered and unpainted wood. Valley carpenter bees prefer partially decayed live oak,
deciduous oak, eucalyptus, and other hardwoods. The California carpenter bee nests in
incense cedar and redwoods. The Mountain carpenter bee is recorded as nesting in
structural timbers.
Male carpenter bees tend to be territorial
and often become aggressive when humans approach, sometimes hovering a short distance in
front of the face or buzzing one's head. Since males have no stinger, these actions are
merely show. However, the female does have a potent sting which is rarely used.
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