It was a regular Saturday morning at my house when my three-year-old let out a searing shriek from the living room, where a ladybug had dive bombed into her Cheerios. We had noticed an uptick in these insects crawling around on the interior walls and window sills of our house, and the invasion had been unpleasant, but this particular infraction had crossed a line.
This same scene, perhaps minus the cereal swimming session, has been playing out in homes and buildings around the state. In recent weeks the University of Vermont Extension Plant Diagnostic Clinic has received many calls, emails and samples regarding insects that have invaded homes, including the ladybug – an Asian multicolored lady beetle, to be exact.
“People are just freaked out by insects in general, especially insects in homes,” says Ann Hazelrigg, a plant pathologist with UVM Extension. “I think they are most concerned that they are structural pests and will harm the home, or cause damage to humans or pets, which they don’t.” Hazelrigg says the Asian multicolored beetle can cause a small bite, which she describes as more surprising than painful.
The Asian multicolored lady beetle was introduced by the U.S. Department of Agriculture as a biological control agent because it is an important predator of aphids and scale insects.
A multicolored Asian lady beetle. (Scott Bauer, USDA, Bugwood.org)
“It does seem the ladybugs have exploded since being introduced,” says Hazelrigg. However, she says these numbers may not be attributed to the earlier introductions, but rather to a more recent introduction via shipping freight. According to Penn State University, “the beetle’s recent population increase in Louisiana, Pennsylvania, and other northern states may not have resulted from the earlier USDA releases, but instead, are thought to be from a new source that was accidentally introduced in New Orleans from an Asian freighter.”
Asian multicolored lady beetles, which are slightly larger than native lady beetles, are oval, yellow to red in color and can have no spots or up to 19. These beetles become a nuisance on sunny south or southwest sides of houses in the fall and can inundate homes from September through April. It is not uncommon for thousands of beetles to congregate in attics, ceilings and wall voids and, due to the warmth of the walls, will move around inside these voids and exit into living areas. In addition to the small beetles sometimes biting, they exude a foul-smelling defensive chemical that will sometimes cause spotting on walls and other surfaces.
The Asian multicolored lady beetle is one of four common home invaders in Vermont. The other three are western conifer seed bug, brown marmorated stink bug, and the boxelder bug. They all typically search for protected sites, including homes, to overwinter and thus become annoyances in and around houses. However, none of these breed in the house or cause any damage to humans, pets, food items, or structures, says Hazelrigg.
The largest of the four is the western conifer seed bug, which feeds primarily on the seeds and developing cones of several species of conifers and their respective hybrids. They have been expanding their range eastward, which today extends across the northern U.S. into Canada. “The western conifer seed bug’s consumption of Douglas-fir seeds and seeds of various other species of pine can result in a loss of seed crop,” Hazelrigg said.
Adults are about 3/4-inch long and brownish in color, with alternating light and dark bands running along the outer wing edges on the sides of their abdomen. The lower hind leg is widened on each side of the leg and looks like a tiny leaf has been attached. The insects move slowly but can fly and often make buzzing sounds when airborne. They will give off a pungent odor if handled.
Another home invader that can be confused with the western stink bug is the brown marmorated stink bug. “There is not much good about the brown marmorated stink bug,” said Hazelrigg. “It has caused millions of dollars of damage in more southern regions on fruit and vegetable crops.”
Brown marmorated stink bug. (Susan Ellis, Bugwood.org )
This insect was introduced to the U.S. from Asia in 1996 and has become a destructive fruit and vegetable pest in the Mid-Atlantic states, where some homes have been invaded by thousands of this nuisance pest. In Vermont, numbers have been low, and they have been noted only as home invaders, as opposed to crop pests.
This stink bug is shield-shaped and about 5/8-inch long with a mottled brownish grey color. The next to last (fourth) antennal segment has a white band. Several of the abdominal segments protrude from beneath the wings and are alternatively banded with black and white. The hind leg is cylindrical, unlike the western conifer seed bug.
The boxelder bug is more colorful, like the ladybug. Adult boxelder bugs are flat-backed, about 1/2-inch long, 1/3-inch wide, and dark brownish-black with three lengthwise, red stripes on the thorax (area behind the head). Beginning around October, adults and large nymphs congregate in large numbers, primarily on the southwest side of the house (and on boxelder trees) and then begin migrating to a place conducive to overwintering.
The adults overwinter by hiding in cracks and crevices in walls, in door and window casings, around foundations and other protected places. Removing boxelder trees may decrease their numbers in the fall, although they can fly up to two miles.
When it comes to keeping these insect invaders out of your house, a vacuum cleaner easily does the trick. Hazelrigg said it is the most efficient method of collecting
An adult boxelder bug (Whitney Cranshaw, Colorado State University, Bugwood.org _
the insects once in the home, though it is advisable to empty the bag and insects after each vacuuming.
Preventing the insects from entering is another effective method. Hazelrigg says homeownersshould seal cracks around windows, doors, siding, utility pipes, behind chimneys, and underneath the wood fascia and other openings with good quality silicone or silicone-latex caulk. Homeowners can also repair or replace damaged screens on doors and windows and cover attics, fireplace chimneys, and exhaust vents with number 20 or smaller screen mesh.
Exterior applications of insecticides may offer some relief from infestations where the task of completely sealing the exterior is difficult or impossible, Hazelrigg said, but this is usually not warranted.