Adult ladybugs have convex, hemispherical shaped elytra (the hardened wings used to cover the soft flying wings underneath) that can be yellow, pink, orange, red, or black, and usually are marked with distinct spots. This is a type of warning coloration (aposematic coloring), thought to discourage predators. Lady beetles also have another defense: an odorous, noxious fluid that seeps out of their leg joints when the insects are disturbed.

Ladybugs, both adults and larvae, are known primarily as predators of aphids (plant lice), but they prey also on many other pests such as soft-scale insects, mealybugs, spider mites and eggs of the Colorado Potato Beetle and European Corn Borer. A few feed on plant and pollen mildews. One larva will eat about 400 medium-size aphids during its development to the pupal stage. An adult will eat about 300 medium-size aphids before it lays eggs. About three to ten aphids are eaten for each egg the beetle lays.