The Asian lady beetle: boon or bane?

StoryImage( ‘/Images/Story//Auto-img-111159851413965.jpg’, ‘Image by M. Kmetz courtesy of’, ‘The Asian lady beetle.’);
StoryImage( ‘/Images/Story//Auto-img-111159862415914.jpg’, ‘Photo courtesy of’, ‘The pattern of dark spots on the back of the Asian lady beetle are quite varied.’);

Most of us in northern Illinois, as well as the rest of the country, are familiar with the Asian lady beetle (Harmonia axyaridis). This is the bug that has the annoying habit of gathering in great numbers on the sides of our dwellings in the fall and wandering inside to make a real nuisance of themselves. It is about one-third of an inch in length, dome-shaped, yellowish to reddish orange in color and usually with a pattern of black spots on its back.

There is some misinformation concerning how this undocumented alien gained entrance into the United States. In some publications, it is stated it jumped a Japanese ship in the port of New Orleans in the late 1980s and spread far and wide. The truth of the matter is, it was introduced as a biological control agent (the use of one species to control another) by the U. S. Department of Agriculture in Louisiana and Mississippi in 1979 and 1980. It adapted to its new environment, and now has spread to most parts of this country.

There are approximately 475 different species of native lady beetles in the U. S., and most of them are considered to be very beneficial to man. The primary diet of both the larvae and the adults consists of soft-bodied insects such as aphids, scales, and plant lice, which can harm a variety of crop and ornamental plants. A few have gone astray, however, and feed on plants. The Asian lady beetle consumes its share of harmful insects, especially aphids that attack soybeans. It has been estimated that each adult or larva may consume as many as 50 to 100 aphids in a single day.

There are, however, two major differences between our native species and the Asian variety. As winter approaches, the natives find a natural place to pass the winter under leaves or other debris, but the Asian bug is attracted to the warmth of a house or building with the idea of sharing our heated structures during the cold months. And the ladybug from the Far East will sometimes pinch your exposed skin with its mandibles, and they may leave an unsightly smear and a distinctly unpleasant odor if agitated or crushed. There is no question that this alien, introduced beetle is of value as a biological control agent, but one wonders if its contribution to agriculture outweighs its nuisance potential at certain times of the year.

The value of ladybugs to mankind has long been recognized. During the Middle Ages, it was dedicated to the Virgin as “The Beetle of our Lady.” They were then known as “Beetles of the Blessed Lady,” which today has been shortened to lady beetles, lady birds, and lady bugs. In Sweden, the beetles are called “Virgin Mary’s Golden Hens,” and in parts of France they are known as “Cows of the Lord.” It is interesting to note that the former First Lady, Mrs. Lyndon B. Johnson, acquired her lifelong nickname when seeing her as a baby, someone remarked, “She’s as cute as a lady bird.”

The prestigious Entomological Society of America has given this beetle the official name of “multicolored Asian lady beetle,” but a less formal name for the pest is “Halloween lady beetle” because of its pumpkin-orange color and its seemingly exploding populations around Halloween.

In general, insecticides are ineffective in the control of populations of this pest. The best technique for managing them is to prevent their entry into houses by sealing cracks around doors, windows, siding and utility pipes. Holes in screening should be repaired using regular window screening.

Somehow or other, however, these vermin seem to find a way of penetrating our defenses against them and get into the house. Then they should be collected with a broom or dust pan and returned outdoors. A vacuum cleaner may also be used to remove them from the premises.

When using a broom and dustpan care must be taken not to unduly alarm the insects. All lady beetles have the annoying habit of discharging a foul-smelling substance from their leg joints when they are disturbed. This fluid (actually the insect’s blood) can stain paint, walls, and fabrics.

The benefits and malevolencies resulting from the multicolored Asian lady beetle being introduced into this country, in my opinion, just about balance each other out. In any event, we are just going to have to learn to live with their sometimes annoying presence.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

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