Asian Lady Beetle
The Asian lady beetle (not to be confused with the indigenous American ladybug) is an invasive species of the Coccinellidae family introduced into the United States in 1988 for the purpose of reducing native aphid populations. Since 1988, they have spread throughout North America, in most places displacing the native ladybug populations to become the dominant Coccinellidae beetle. Because of their destruction of plant life and their aggressive tendency to bite, Asian lady beetles are commonly considered a nuisance pest.
Biology of the Asian Lady Beetle
The Asian lady beetle (Harmonia axyridis) hibernates in crevices and other cool, dry places during the winter, only becoming active when the temperature begins to rise about 50 °F. The beetles are often seen congregating in large groups. These groups are “summoned” by a pheromone call put out by the beetles in the autumn. The like to congregate together in sunlit areas to warm themselves – indoor heating may even cause some of them to become active during the winter months. Favorite places to congregate are on the upper regions of window panes and dark screening material. The beetles have good eyesight and a very developed sense of location and will return to a favored sunning spot if removed.
The Lady Beetles natural prey is the aphid, which they eat in large numbers. This can be beneficial; in fact, the Asian lady beetle was originally introduced into the United States to control aphid populations in pecan orchards. They will also feed on spider mites, the jumping plant louse, mealy bugs, leaf beetles, weevils and moths. In addition to this, they will occasionally feed on pollen and nectar and will even cannibalize other Lady Beetle larvae if other food is unavailable.
The Asian lady beetle has a defensive odor it can secrete when it is under attack. This odor comes from a chemical released from their legs. The chemical is very highly concentrated has a foul, unpleasant odor detectable even by humans. This can result in an unpleasant smell if the bug is crushed. It has also been known to stain curtains/carpet or other fabric it is released upon.
Asian lady beetles breed in temperate climate conditions, especially in the spring and early fall (they may also breed in the summer, but frequency of breeding goes down the higher the temperature gets). Lady Beetles are very prolific: a single female is capable of laying 3,800 eggs per season in batches of 20 to 30 per day. Adults may live anywhere from 90 days to three years, depending on temperature. As fall begins to turn to winter, they will migrate to overwintering locations, often the sides of buildings facing the south or west; they also seem to prefer to land on surfaces that are white or light-colored. They typically seek the warmth of human structures for their period of winter inactivity.
The Lady Beetle as a Pest
Though the Asian lady beetle does not do any damage to property (aside from the possibility of staining curtains/fabric with their secretions), however their invasion of homes by the hundreds and their congregating on window panes ensures that they wear out their welcome rather quickly.
Asian lady beetles are much more aggressive than their indigenous American counterparts and will bite if provoked or moved. Their bites are not poisonous or extremely painful, but in some cases, the bite of the Asian lady beetle can can an allergic reaction leading to rhinoconjunctivitis, commonly known as “pink-eye.”
Asian lady beetles are also considered an invasive species due to their displacement and destruction of native species of Coccinellidae. In many places in the United States, Asian lady beetles have displaced the native American lady bug by competing more aggressively for resources. In Michigan, native lady bug populations have been severely threatened in Livingston County, the greater Ann Arbor area and throughout southeast Michigan.
To get rid of Asian lady beetles, call Creature Control at 1-800-441-1519. Our experienced pest control technicians can help you keep your home lady beetle-free!
Ladybug or Asian beetle?
It can be very difficult for a non-entomologist to distingusih between the indigenous American ladybug and the Asian lady beetle. Both look a lot alike and are members of the Coccinellidae family and both exhibit similar behaviors. There are a few ways to tell the two apart, however:
- Asian Lady Beetle: Has a very distinctive white “W” shape on its pronotum, the area immediately behind the head.
- American Ladybug: Has a shiny black pronotum with two tiny white circles.
- Asian Lady Beetle: Their dome is usually orange, tan or yellowish with black spots.
- American Ladybug: Domes are a rich, scarlet red with black spots.