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.
source: Nat Geo