Science / Medicine : Food Is a Mirror Image for Some Caterpillars

There’s a new twist to the maxim “You are what you eat”--caterpillars that look like what they eat.

In findings published last week in the journal Science, researcher Erick Greene of UC Davis said he discovered that certain caterpillars mimic either the flower or the twig of an oak tree. Caterpillars that eat catkins--fuzzy, yellow oak flowers that bloom in the spring--are yellow with green spots dotting their rough backs in imitation of catkin markings, Greene said.

Caterpillars that hatch in the summer after catkins are gone eat mainly oak leaves and young twigs and grow into smooth, gray-green twig imitations.

The caterpillars also displayed different behaviors that help them hide from hungry birds. Spring caterpillars take refuge among flowers, while summer caterpillars nestle among leaves or twigs. The catkin and twig caterpillars eventually form cocoons and emerge as the same type of moth, known to scientists as Nemoria arizonaria.