Yellowjackets are commonly confused with honey bees. Yellowjackets
are the same size as honey bees, but have bright yellow and
black stripes and very little hair. Honey bees tend to be
covered with pale yellow fuzzy hairs without a distinctive
stripe pattern. Popular cartoon depictions of honey bees are
often misleading...and look more like yellowjackets than the
honey bees they portray.
two common species of yellowjackets in the midwest are the eastern
yellowjacket which usually nests in the ground, and the German yellowjacket
that has a habit of nesting in wall voids of structures. Yellowjacket
workers, the most commonly encountered yellowjackets, are about
1/2 inch long. The queen is about 3/4 inch long.
Yellowjackets, like other social insects, have a caste (division
of labor) system. Each nest has a queen whose purpose is to reproduce.
Male yellowjackets fertilize the queen, and sterile female workers
find food, take care of the queen, defend the nest, and care for
queens begin building nests in the spring (May). Depending on the
species, she will locate a hole underground, often an abandoned
rodent burrow, or in a structure and construct a golf ball sized
nest of paper that is made by mixing wood fibers with her saliva.
She lays eggs and cares for the grub-like larvae in the nest. The
first generation of sterile female workers emerge in June and assume
the care of the nest which allows the queen to concentrate on reproduction.
Yellowjacket adults feed on nectar, fruit juices, sap and other
liquids and provide insects and carrion to the larvae. The population
of worker yellowjackets increases during the summer and peaks in
early to mid-August. Nests may contain 1,000 to 5,000 workers and
may measure three to four feet in diameter.
late summer into early fall the queen produces queen and male yellowjackets.
Each nest can produce thousands of new queens. Queens and males
swarm from the nest and mate. The males, workers, and old queens
die as winter approaches. Newly mated queens seek overwintering
sites in protected places such as logs, under bark or leaf litter,
and occasionally in structures. They remain dormant through the
winter and begin the cycle once again in the spring.
Yellowjackets are beneficial insects in the sense that they pollinate
plants and feed other insects and carrion (dead meat) to their larvae.
Many times they will prey on insects that we identify as pests.
Unfortunately, their ability to sting makes them a considerable
health concern. Yellowjackets alone are responsible for about one-half
of all human insect stings. The stings of social wasps, such as
yellowjackets, have evolved as a defense mechanism. The only purpose
for the sting is to inflict pain. Yellowjackets are easily provoked
and, unlike honeybees, can sting more than once. They will attack
in force if their nest is disturbed. Unless a person is allergic
to yellowjacket venom, stings are rarely life threatening.
Yellowjackets are most frequently encountered when they scavenge
for food. Their habit of feeding on nectar and sugar can create
a nuisance. Yellowjackets locate places where sweet food products
have been served throughout the summer such as picnic facilities,
ice cream stands, or soda fountains. In the fall, these locations
usually have extremely high yellowjacket populations. By avoiding
these areas, or eating in screened areas, contact with yellowjackets
can be reduced.
are attracted to open cups and cans of soda and other sweet liquids.
They are also attracted to open cans of garbage, bright flowery
clothing, and floral scented perfumes. All outside garbage cans
must be kept clean and well covered, to reduce yellowjacket problems.
Contact with the wasps can be decreased by reducing these attractions
at picnics and other outings. In situations closer to home, the
elimination of overripe fruit from gardens and orchards will dramatically
decrease the number of scavenging yellowjackets. Holding gatherings
indoors and using screens on windows will also help avoid yellowjacket
are a variety of traps on the market that claim to attract yellowjackets.
These traps are baited with the scent of rotting fruit or other
odors equally as appetizing to the yellowjackets. It is questionable
whether these traps can out-compete the natural and man-made attractants
described above. However, it is certain that through proper sanitation
and removal of natural and man-made attractants, yellowjacket contact
can be reduced. However, in situations where the potential for repeated
human contact exists, other management methods may be necessary.
Management of each species of yellowjacket differs because of their
nesting habits. Both species do not reuse their nests, therefore
what was a problem this year may not occur next year. Caulking cracks
and crevices in structures in winter and early spring, after the
nests have died, will prevent German yellowjackets from constructing
nests inside buildings. Openings to active nests should not be caulked.
control for ground-nesting yellowjackets consists of drenching the
exit hole with an approved insecticide and plugging the hole with
treated soil or cotton balls. Yellowjackets that are not killed
by the initial treatment will be killed by chewing on the treated
cotton ball or tunneling through the soil. Yellowjacket entrance
holes in buildings can be treated with approved insecticide dusts.
As the yellowjackets walk through the dust they pick it up on their
legs and transport it into the nest. When yellowjackets groom themselves
they ingest the dust on their legs. It may take up to a week for
the colony to die and repeated chemical applications may be necessary.
When the entrance hole of an active nest is in a building, the hole
should not be plugged with the insecticide or caulked. The yellowjackets
may decide to chew through the soft inside wall rather than chew
through the insecticide or caulking material.
chemical control measures at dusk or dawn when the wasps are in
their nest. Wear protective clothing when attempting to eliminate
the nests, such as long sleeved jackets, gloves, and pants. Tape
the wrists and ankles to the clothing, to prevent the wasps from
getting underneath the clothes. A bee veil or other enclosed form
of face and neck protection should also be worn. Yellowjackets will
defend their nest, so to avoid being attacked, use a flashlight
covered with red cellophane when applying the insecticide at night.
Yellowjackets are unable to see red. In sensitive locations, or
where control has not been effective, professional pest control
operators should be consulted to handle the problem.
more information on managing yellow jackets and chemical recommendations,
see the University of Illinois Urban Pest Management Handbook or
contact your unit office of the University of Illinois Cooperative
States Research, Education, and Extension Service.
by Entomologists at the University of Illinois and Illinois Natural
History Survey. For additional copies, contact your unit office
of the University of Illinois Cooperative Extension Service.
Illinois 1995. Issued in furtherance of the Cooperative Extension
Work Acts of May 8 and June 30, 1914, in cooperation with the U.S.
Department of Agriculture. Dennis R. Campion, Interim Director,
Cooperative Extension Service, University of Illinois at Urbana-Champaign.