A Foreign Lady (Bug)
By Wayne Bierbaum
Several times a week, I walk around my yard and do a survey of bugs. It is not a formal count but I am interested in how many beneficial insects are in residence.
This week, I found five small Chinese praying mantis, but no native Carolina mantis, and a dozen ladybugs. Strangely enough, none of the ladybugs had spots. Initially, I thought that the ladybugs were just young and would grow up and develop spots. It turns out that, like the praying mantis, an Asian species of ladybug has been introduced by well-meaning entomologists.
At the turn of the 20th century, aphids were damaging pecan trees. Our native seven-spotted ladybug was not inclined to live so high above the ground but the tree-loving multicolored Asian ladybug did, so they were studied and introduced to the U.S.
It was a somewhat successful experiment, and from 1916 to 1985 it was introduced at various locations in the U.S. for control of aphid infestations in an assortment of crops. It wasn’t until 1988 that a population was found to have established itself in Louisiana. By 1993, the ladybugs were found in Virginia. It is now the most common ladybug species in Maryland and quite common throughout the Midwest and East Coast.
The Asian ladybug is also known as the Harlequin ladybug because it can be found in many colors, with or without spots. The shell can range from black to light yellow with zero to 15 spots. It is larger than the native species and more resistant to pesticides and fungal disease. The Asian ladybug also commonly has a fungus living in it that is deadly to the native species. They are also known to eat native ladybug eggs and larvae.
Their life cycle involves a wingless larval stage that is black with yellow spots and described as alligator-shaped. The larvae are very hungry and probably eat more aphids than an adult beetle. After it eats enough, usually within three weeks, the larvae molt into adults, and continue to consume aphids and are able to fly to other areas to feed.
When fall comes, the Asian ladybug will look for a place to spend the winter. When they find a likely location, they will release a pheromone that attracts more and more bugs. They are known to invade buildings by the thousands. The adult beetles are actually known to have bitten people. It is said that they are trying to get salt but they really seem to be taking a quick taste—a sharp nip. So having them invade your home could end up with you getting a few bites. The best way to prevent them from invading is to make sure all cracks are sealed with caulking.
The native seven-spotted ladybug is still around and the hope is that it can somehow live in harmony with the multicolored Asian ladybug. I went back to look at all the ladybug photos I have taken over the past five years and only one out of 10 were of a native seven-spotted ladybug.