Carpenter Bee |
Carpenter Bee
Two species of Xylocopa, or carpenter bees, occur in
the eastern U.S. Xylocopa virginica is found from Maine
to Wisconsin and south to florida and Texas. In Michigan
it appears to be restricted to the southern half of the
state. Xylocopa micans Lepeleter occurs in the
southeastern states. Carpenter bees are widespread in
their distribution, but are seldom abundant in any given
locality.
The adult carpenter bee resembles the common bumble
bee. Carpenter bees are large (20-30mm), robust, and with
a shiny, bluish-black abdomen. Bumble bees, on the other
hand, have a hairy abdomen that is mostly yellow.
Adults excavate nests in wood. Softwoods (pine,
redwood, fir, cedar, and spruce) are preferred, but they
have been seen nesting in hardwoods (willow and oak). A
"nest" consists of a round entrance hole (0.5 inch
diameter by 1.5 - 2 inches deep) and a system of tunnels
oriented along the grain of the wood. Tunnels range in
length from a half foot to several feet (after years of
use). The bees cut one half inch per day to open the
entrance hole, and then move at a faster pace as they cut
the tunnels with the grain.
Nests are located in porches, eaves, fascia boards,
garages, sheds, carports, fences, window trim, lamp
posts, and other wood objects. Nests are most likely to
be southern or eastern in aspect. They tend to avoid wood
that is painted, whitewashed or covered with bark.
Juvenile (unmated) adults of both sexes overwinter in
the tunnels. They become active when temperatures reach
the 70's in the spring. Mating, accompanied by a strange
"bobbing dance" by the male, occurs in April.
The bees clean and enlarge the nest. They seem to
prefer this to establishing new nests. Therefore, nests
may be used by many generations of bees. Some nests have
been known to have been in use for 14 years. The females
prepare a series of brood cells in the tunnels, providing
each with food ("bee bread" - a mixture of pollen and
nectar), an egg, and a partition of chewed wood. Most
females produce 6 to 8 young. The larvae develop from May
to August, emerging in September. The oldest bee,
developing at the end of the tunnel, emerges first and
must cut through all the partitions and crawl over the
other developing bees. There is only one generation per
year.
There are two principle concerns about the activities
of carpenter bees. One concern is over the possibility of
stings. However, this is actually of minor consequence
since the females (males can't sting) are very hesitant
to sting, and in fact must be held to provoke a sting. In
addition, they are mild stings.
The second concern deals with wood damage. It is
generally more of an aesthetic problem since they rarely
nest in structural timbers. Damage is most severe in trim
and decorative wood on the exterior of the building.
Other concerns include stains of excreta, the buzzing
flight of the adults, the noise of nest construction, and
the attraction of (hungry) woodpeckers.
Carpenter bees are not particularly important as
pollinators. In addition to woodpeckers there are two
species of bee flies (Diptera: Bombyliidae) that are
natural enemies of the carpenter bee. The flies deposit
their eggs in the entrance of the tunnel and the maggots
parasitize the bee larvae.
Carpenter bees are best controlled by placing ready
to use diazinon, or contact sprays of pyrethroids in the
tunnels. After thoroughly treating, plug the entrance
with a dowel of the appropriate size. It may be helpful
to treat the sites used, or most likely to be used, with
one of the residual insecticides mentioned previously.
This should be done in the spring prior to the time when
the bees begin nest construction.
For a complete listing of suggested control options
for all home, yard and garden insect pests contact your
local Extension Service, found under local government in
the phone book.
Read and follow instructions on the pesticide label.
Heed all warnings. Check with your physician if you have
any concerns regarding your personal health risk.
Revised by Tom Ellis, M.S., Department of Entomology |
This information is for educational purposes only. References to
commercial products or trade names does not imply endorsement by MSU Extension
or bias against those not mentioned. This information becomes public property
upon publication and may be printed verbatim with credit to MSU Extension.
Reprinting cannot be used to endorse or advertise a commercial product or
company. This file was generated from data base 02 on 02/27/01. Data base 02 was
last revised on 12/04/98.
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