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:
(1)
Bumble bees (Apidae) have hairy abdomen with yellow markings, 2nd
submarginal cell somewhat rectangular to pentagonal, and hind wings lack a
jugal lobe. (2) Some robber flies (Diptera: Asilidae) which resemble bumble
bees, with only 1 pair of wings. (3) Some hawk moths (Lepidoptera:
Sphingidae) 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. californica 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 1st abdominal
segment has whitish hairs.
- The valley
carpenter bee, X. varipuncta 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 10 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.
CONTROL:
Carpenter bee
control consists of treating each individual gallery with an appropriately
labeled pesticide. Dusts, wettable powders, microencapsulated, and aerosol
residual formulations work best. Aerosol injection systems are probably the
most efficient and safest way to treat galleries, especially when on a
ladder. Do not seal the treated gallery for 24-48 hours so that the female
has time to be exposed to a lethal dose. Newly matured bees should contact a
lethal dose before they can emerge.
Carpenter bees rarely
attack painted wood. They can be discouraged from using wood by applying an
appropriately labeled repellent material such as one of the pyrethroids, and
microencapsulated or wettable powder formulations are best.
