Multicolored
Asian Lady BeetleMulticolored
Asian Lady BeetleAs the weather turns cool, insects begin to look around for a nice place to settle in for the winter. Unfortunately, a few species may choose your house. The multicolored Asian lady beetle is one such invader that starts looking for lodgings in mid-October.
Harmonia axyridis
is a yellow to orange colored lady beetle that often is seen in large
congregations on buildings around the end of October – hence one of its common
names, the Halloween lady beetle. The multicolored Asian lady beetle is the
preferred common name for this lady beetle introduced from Japan for control of
tree-inhabiting aphids. The USDA made several releases
throughout the eastern United States in an attempt to introduce this beetle into
North America. It took a long time for releases made in Louisiana and
Mississippi in 1979 and 1980 to become established and spread, but by 1994 it
was found in Alabama, Georgia, South Carolina, and Florida. It can now be found
in many locations throughout the Midwest. This species was first recorded in
Wisconsin in 1992, but it has quickly spread around the state.
The adult lady beetle is quite variable in appearance.
Individuals can be any color from a pale yellow-orange to a deep orange-red, and
have from no to more than 20 black spots. They are very prolific and may live up
to three years. The bright yellow eggs are laid in clusters of
about 20 on the undersides of leaves.
The eggs hatch in three to five days, and
the larvae feed up in the trees for 12 to 14 days. They then pupate on the
leaves and adults emerge in five to six days.
The multicolored Asian lady beetle inhabits various trees, including maple, walnut, willow, and oak, and feeds on various aphids, certain scales, and a few other insects. It is an effective predator of aphids on pecans, pine trees, ornamental shrubs, roses, and other plants. In many areas pecan growers no longer need to spray their trees for pecan aphid because this lady beetle has done such a good job of biological control. Beetle populations tend to explode when there is an abundance of aphids, often eliminating the local aphid population.
Even though this lady beetle is an important biological control agent, it can become a nuisance when they aggregate in large numbers on homes or other buildings. For several days during autumn they typically cluster on sunny, southwest sides of light-colored rock outcroppings or structures (especially clapboard siding). In their native habitat these colonies would find refuge in crevices of cliffs and rocky hillsides to hibernate. Here, they will also move into leaf litter, underneath boards or logs, or other protected areas after the first frost.
Homeowners, however, complain when there are
thousands of beetles covering their house, they have to walk across piles of
them on the deck, they get in picnic food and drinks, "swarm" like
bees and land on people, and especially when the beetles get in the house. Outdoor aggregations
may leave voluntarily after a few days or weeks, but, as experienced crevice
finders, they often find their way through tiny cracks into the walls, around
uncaulked window frames, into attic areas, and other areas. When warm days bring
them out exploring, if they go the wrong direction, they end up in the house.
The best way to prevent beetles from becoming
uninvited houseguests is to seal cracks around windows, doors, siding, utility
pipes or other openings with a good quality caulk. Replace or repair damaged
screens, and install screens over roof vents. Sprays are a temporary secondary
solution. It's important to act quickly when an invasion begins because the bugs
can be almost impossible to kill or remove once they've found a snug spot to
spend the winter.
The best way to deal with lady beetles in the house is to vacuum them up (but don't use an attachment with a beater bar, since it will crush the beetles and may stain carpets). They can also be swept up with a broom and dustpan and be deposited outside well away from the house. Killing them with insecticides, squashing them, or handling them may result in orange stains on walls and fabric. When stressed the lady beetles secrete a harmless, but staining, orange substance. This liquid is actually blood that comes our of the joints of the legs – a phenomenon called reflex bleeding (all lady beetles do this when stressed).
– Susan Mahr, Department of Horticulture
