Feature Article April 24, 2002
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The Southern Lady Beetle - Harmonia axyridisby Jean GriffinThousands of this beetle have been found over the last 2 or 3 years around our homes. Where did they come from? The US Department of Agriculture made several releases throughout the eastern United States in an attempt to introduce this beetle (originally from Japan) into North America in an effort to control many species of injurious soft-bodied insects such as aphids, scales, and other pests. It took a number of years for the introduction to succeed, but once it did, their numbers exploded, and they are now widespread over North America..
It is believed that females overwinter in protected sites unmated, with the majority of the population mating later in the spring. Eggs generally hatch in 3 to 5 days. The larval stage lasts 12 to 14 days, and the pupal stage, which takes place on leaves, lasts 5 to 6 days. In cool spring weather, development from egg to adult can take 36 days or longer. After emergence, adults can live as long as 2 to 3 years under optimal conditions. An adult is capable of consuming 90 to 270 aphids per day, and each larva can consume 600 to 1,200 aphids during its development. H. axyridis is a promising biological control agent of several insect pests on a wide variety of ornamental and agricultural crops. Its large, and even explosive, populations are probably caused by the massive abundance of prey (predominantly aphids and scales), apparent lack of competition from native lady beetles, and apparent lack of native natural enemies. Scientists predict that multicolored Asian lady beetle populations will become more balanced when its prey numbers decrease and Harmonia itself falls prey to native natural enemies.
As a result of their overwintering behavior, with its habit of invading houses and buildings in large numbers while searching for protected sites in the fall (mid-October to early November) and appearing again on warm, sunny days in February and March, they are a nuisance.
First of all, they will do no harm. Their droppings can be messy, however, especially early in the fall when they first enter the building. When people disturb them or try to remove them by sweeping, with vacuum cleaners or with other tools, the foul odor spoils the air, and yellow spots on people, expensive furniture and drapes result. They will not reproduce indoors, they won't feed on anything, and will leave in the spring if given the chance. What's more, your yard trees will be forever grateful.
Despite their overwintering behavior, H. axyridis are very valuable as natural enemies of many insect pests and should be tolerated and conserved when possible.
This article has been taken from various sources