Found in wet forests and shrublands, 18 known species of Eupithecia in Hawaii are unique from all other members of the genus: unlike their herbivorous brethren, these Hawaii Eupithecia are carnivorous and capture live animal prey. All are species of inchworm, tiny (about an inch!), and camouflage themselves on sticks and fern fronds where they wait for unsuspecting flies, spiders and crickets to pass by. They anchor themselves with their rear prolegs and strike with six front tarsal claws when their rear setae (sensory bristles) are touched.

Hawaii’s killer caterpillars evolved to fill the ecological niche filled by insects, such as the praying mantis, elsewhere. They attack with speed, only about 0.1 second is required, and devour their prey alive.