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Down On My Luck: Why Are The Ladybugs Biting?

As a child, my grandmother always said it was good luck to have a ladybug land on me. However, in recent years, it has been easy to confuse these lucky bugs with their similar looking relative, the Asian lady beetle. The friendly little insect most of us grew up with, commonly referred to as the ladybug, is the Coccinella septempunctata. This so called “bug” is actually a beetle that can be very beneficial to gardeners by consuming fruit flies, thrips, and other bothersome plant pests. What we now see in mass numbers are Asian lady beetles. This beetle is a non-native insect, originally from northeastern Asia. It was introduced to the US in an attempt to control the spread of aphids, or plant lice. Biologists had unsuccessfully attempted to bring these beetles here since the early 1900s, but they finally took root in Louisiana in 1988. Since then, the insect has spread throughout the US and has succeeded in controlling aphid populations. Most people see these beetles as a problem once fall arrives. The beetles congregate in our window sills and inside the walls of our homes, trying to find a cool, dry, confined space to hibernate during the winter. They again become an annoyance in the first warm days of winter or early spring when they start to crawl around again. But another reason people tend to not like these Asian lady beetles is because of the assumption that they bite. However, bites are uncommon and often the stinging sensation we feel is actually caused by small spurs on the beetle’s legs pricking skin as they move. When they do bite, it is likely that it is a hot day and the beetle is trying to “drink” one’s perspiration using its mouthparts, which may cause a pinching sensation. But don’t worry, these beetles don’t carry disease, nor do they have any toxins. So how do you tell the difference between the native and the foreign beetles? This can be a little confusing because although the multi-colored Asian lady beetles and ladybugs all have the same shape, they vary in color from yellow to orange to red. Despite this color range, there is one characteristic that all Asian lady beetles have and ladybugs lack: a distinguishing mark on their pronotum, the small section that separates the head area from where the wing covers start. If it is an Asian lady beetle, there is a mark on the pronotum that looks like a “W” or “M” depending on whether you are looking at it from the front or the back. So next time you see a “ladybug,” look for that mark. If you don’t see it, you’re in luck!