Many people are fond of ladybugs because of their colorful, spotted appearance. But farmers love them for their appetite. Most ladybugs voraciously consume plant-eating insects, such as aphids, and in doing so they help to protect crops. Ladybugs lay hundreds of eggs in the colonies of aphids and other plant-eating pests. When they hatch, the ladybug larvae immediately begin to feed. Ladybugs are also called lady beetles or, in Europe, ladybird beetles. There are about 5,000 different species of these insects, and not all of them have the same appetites. A few ladybugs prey not on plant-eaters but on plants. The Mexican bean beetle and the squash beetle are destructive pests that prey upon the crops mentioned in their names.
Spots and Coloring
Ladybugs appear as half-spheres, tiny, spotted, round or oval-shaped domes. They have short legs and antennae. Their distinctive spots and attractive colors are meant to make them unappealing to predators. Ladybugs can secrete a fluid from joints in their legs which gives them a foul taste. Their coloring is likely a reminder to any animals that have tried to eat their kind before: "I taste awful." A threatened ladybug may both play dead and secrete the unappetizing substance to protect itself.
Infestations and Impacts
In the United States, ladybugs usually begin to appear indoors in the autumn when they leave their summer feeding sites in fields, forests, and yards and search out places to spend the winter. Typically, when temperatures warm to the mid-60s F (around 18 °C) in the late afternoon, following a period of cooler weather, they will swarm onto or into buildings illuminated by the sun. Swarms of ladybugs fly to buildings in September through November depending on location and weather conditions. Homes or other buildings near fields or woods are particularly prone to infestation.
After an abnormally long period of hot, dry weather in the summer of 1976 in the UK, a marked increase in the aphid population was followed by a "plague" of ladybirds, with many reports of people being bitten as the supply of aphids dwindled. The presence of ladybugs in grape harvests can cause ladybird taint in wines produced from the grapes.