Every so often throughout the winter, I become aware of a lady beetle waking up from her diapause to see if it’s spring yet. She’s been sleeping with her friends in odd corners of the house, with a few holing up in the can lights in the kitchen. They fall on the floor. The dogs ignore them. The vacuum sucks them up. No particular problem this year.
What do you call these little oval-shaped beetles with their domed backs and penchant for eating soft-bodied insects like aphids and their relatives? In Europe they’re called ladybirds. The name apparently came from the seven-spotted lady beetle which is the color of red that was used in paintings of the Virgin’s robes. The seven spots were said to be representative of her seven joys and her seven sorrows. The beetles were therefore called “Our Lady’s Birds,” or ladybirds for short. We apparently adapted the term to ladybug, although they are not true bugs. So it appears that the terms ladybird, ladybug and lady beetle all point to the same family of beetles known scientifically as Coccinellidae. Some 6,000 species of lady beetles have been identified, with at least 30 species in Iowa. Fossil records on their relatives date back 53 million years.
One species that has drawn a lot of attention in recent years is the multi-colored Asian Lady Beetle (Harmonia axyridis). My first major encounter with them was a cool fall day the year my house was being built. Hordes of these beetles were flying around me as I sat on the unfinished deck framing. They would land on me and bite me when I smacked them. They would also release a yellow, nasty-smelling fluid from their leg joints that ended up on my hands. The next spring I found columns of these beetles neatly lined up in the inside corner of the deck screens. There were some in the house as well, in the can lights in the kitchen and in the windowsills. They don’t normally bite or sting, and they don’t carry diseases, so they didn’t really hurt anything by overwintering on my deck. In the spring, they took off in search of aphids. It is true, though, that if you smash one on the wall, it will leave a very smelly yellow stain. So, don’t smash them—just catch and release them.
No surprise here, but these beetles are imports from Asia. They are brightly colored orange or red with black spots, and are about a third of an inch long. They have a black M-shaped marking behind their heads which is unique to this species. Their larvae look like tiny alligators with spines, and feast on aphids. The reason I had the rows of adults on the white support posts of my deck is that they can live two or three years, diapausing over the winter. They mistook my deck for the limestone cliffs in their native Asia where they hunker down for the winter. I have seen very few on the deck in the last couple of years. I suppose that the pesticides that kill the soybean aphids and Japanese beetles wreak havoc on the Asian lady beetles as well.
These beetles were brought to the United States to try to control garden pests. The first solid population of them, however, was found in 1986 near the port of New Orleans. So whether they came by accident in cargo from Asia, or were deliberately introduced, they are considered to be beneficial. Larvae and adults alike feed on aphids and other garden pests. One of these beetles can eat 5,000 aphids in its lifetime.
People sometimes confuse these lady beetles with another Asian import—Japanese beetles (Popillia japonica). Turns out they’re not the same. The adult Japanese beetles are green. They feed on the fruits, blossoms and leaves of over 300 different plants. They eat out the leaf tissue, leaving the veins as a skeleton of the leaf. The larvae, which hatch and live underground, eat the roots of grasses, damaging them from below. So where the Japanese beetles are very destructive, the multicolored Asian lady beetles are good neighbors and help keep the aphids under control.
At least thirty species of lady beetles live in Iowa. They are identified often by the number of black spots they have on their red or orange backs. They mostly fly during the day, heading either for a place to overwinter, or a place to lay their eggs where there’s enough food. They can fly for 75 miles at altitudes of 3,000 feet or more at speeds of 19 miles per hour in search of the right places. They breed from late spring to early summer, and can lay eggs six times in a year. Larvae begin eating aphids immediately and, throughout its development, a larva can eat from 600 to 1200 aphids. Adults can eat 100 aphids a day, and some 5,000 aphids during its multi-year lifespan.
The multi-colored Asian lady beetles have become invasive throughout the United States, out-competing native lady beetles. So far, though, there seems to be plenty of aphids to go around.
Photo by Author. Alt text: Asian lady beetle wintering inside the house on a sunny window sash frame. The insect’s shape is an almost perfect hemisphere, with black spots adorning its orange elytra (forewings adapted as wing-cases). On its pronotum (the hard plate covering its thorax), it sports an M-shape mark, typical of this species.