The presence and color of the spots on a ladybug's back are meant to make them unappealing to predators, according to National Geographic. There are more than 5,000 species of ladybug beetles and not all have spots. The presence, absence and number of spots enable naturalists to identify various species of ladybug.
About.com reports that the combination of bright red backs with black spots on ladybugs provides aposematic coloration. This warns predators that the potential prey might be toxic. Bright colors such as yellow, red, black and white contrast with foliage and provide effective danger signals. Aposematism is common in insects. In fact, ladybugs are predators themselves. Gardeners welcome ladybugs because they avidly consume insects that damage plants such as aphids, mites, white flies and scale insects. Ladybugs have short life cycles of about four weeks, so that several generations are born every summer. They typically lay hundreds of eggs within aphid colonies, and when the eggs hatch, the ladybug larvae feed on the aphids.
Some ladybug species are identified by their number of spots. For example, seven-spotted ladybugs have three spots on either side and one spot in the middle. Others have stripes instead of spots. A few species are hard to identify as ladybugs because they are entirely black or gray. Several insect species with similar markings are sometimes mistaken for ladybugs, such as grapevine beetles. It is a common but unfounded myth that a ladybug's spots determine its age, as the spots only indicate the species, according to About.com.