About one in three insects in existence today is a beetle, and they have successfully colonized every sort of habitat. They range from tiny insects less than 1/32 in. in length to tropical giants measuring 7 in. Although beetles vary enormously in both shape and coloration, a major distinguishing feature is their toughened forewings, also known as elytra. These hard forewings protect the larger, membranous hindwings that are folded underneath.
 

Also called oil beetles, the adults produce cantharidin, an oily fluid to deter predators that can blister human skin. Most species are soft, leathery, and black or brown with red or yellow marks. Some are metallic. Most are long and parallel-sided; a few are oval. The elytra vary in length.
 

Blister beetles' eggs are laid in soil. The mobile, first-stage larvae locate and eat the eggs of grasshoppers or bees. Adults are herbivorous.
 

Worldwide, except in New Zeland, mainly in warm, dry areas. On flowers and foliage.
 

Some species are crop pests.