GROUND BEETLES (Carabidae)

Structures with bright lights visible from outside at night are likely to attract six-legged visitors, and larger structures, such as commercial buildings that are often well-lighted at night, are particularly susceptible to invasion by ground beetles. There are many species, but the ground beetles most commonly attracted in large numbers are dull to shiny black, about one-half of an inch long, and somewhat flat in shape.

These beetles are strong fliers that enter structures through open doors, windows and vents, gaps beneath doors and similar openings. By day they are found dead of exhaustion or resting among the surrounding ground cover, mulch, rock and debris, or in soil and pavement cracks. Foundation perimeter treatments with liquid residual pesticides can therefore be an effective control. But the best method is to reduce night lighting by shading or switching off lights visible from outdoors.

Larger ground beetles can bite, pinching the skin. Some release foul-smelling defensive secretions, and some species, known as bombardier beetles (Brachinus and others), release irritating chemicals that explode with a popping noise.

LADY BEETLES (Coccinellidae)

The group of insects known as lady beetles, ladybird beetles and ladybugs, includes several species that arrive at our homes in the fall, often in large numbers, intent on spending the winter with us.

There are several home-invading species; round or oval-shaped beetles, about one-fourth of an inch long, yellow to red in color with black spots. One native species that often enters homes is the spotted lady beetle (Coleomegillafuscilabris). It is an oval, pinkish-red beetle, usually with 10 black spots. The convergent lady beetle (Hippodamia convergens) is commonly sold as a biological control agent for release in gardens, though often ineffective due to its habit of migrating from the release site. Adults are up to one-fourth of an inch long, yellow to orange in color with up to 13 black spots, and white lines that converge behind the head.

Besides being colorful and considered cute, lady beetles are beneficial because they consume large numbers of injurious plant pests including aphids, mealybugs and scale insects. The Asian lady beetle (Harmoniaaxyridis) was thought to be of such value as a predator that it was collected in Asia and introduced across the United States over many years to control pests in orchards and other crops. While it has done its share to save valuable crops, it also invades structures each fall in greater numbers than those of native lady beetles.

The Asian lady beetle is also known as the multicolored Asian lady beetle because its color varies from pale yellow to red-orange. Most specimens have 19 black spots, but some have none. Another identifying character is the black M-shaped marking (think “M” for multicolored) outlined in white on its back just behind the head. The young are typical alligator-shaped lady beetle larvae, red, orange and black in color, with Y-shaped spines covering their bodies.

When disturbed or crushed, the beetles secrete a foul-smelling orange-colored fluid from joints in their legs. This can stain fabrics, carpeting, wallpaper and other household items. In addition, the adult beetles will feed on fruit, especially grapes, but also apples, peaches and berries. They prefer to lap up the juices of damaged fruit, but will bite into and feed on undamaged fruit as well. Similarly, the beetles will bite humans, though the bites are no more serious than pin pricks.

As the Asian lady beetle is a tree-dwelling species that naturally spends the winter in the cracks and crevices of cliffs, multi-story homes and homes on hills near wooded areas are likely to be invaded in the fall.

Lady beetles will often settle down for the winter beneath siding and shingles, in attics, soffits, porches, garages, wall voids, window and door frames. Owners of homes at risk should seal these harborages when practical. Properly timed, preventive treatment of exterior walls and surfaces with liquid residual pesticides may be of value, and is best done by pest management professionals. Once the beetles appear indoors, collect them using a vacuum cleaner.