The spots on ladybird beetles serve as a warning to predators

The spots on a ladybug aren't only for beautification purposes. They also serve as a warning to predators, thereby protecting the insect from predation. 

The bright colors and spots warn would-be predators that the insect is toxic and tastes horrible.

Apart from their colors, another one of the ladybug defenses is the foul-smelling blood they emit. This yellow liquid comes from their leg joints, leaving yellow stains on the surface below. This liquid is toxic to various ladybug predators, protecting these little creatures from harm as predators avoid the seemingly sickly beetle. They also have a third defense mechanism, which is to play dead.