May, 2007

Ilia Underwing

This month's featured animal is the caterpillar of the ilia underwing (Catocala ilia), a rather large nocturnal moth. This larva, which can reach about 3 inches in length, is not particularly abundant but appears in our yard every so often. It feeds on oaks, so we only see it when one ends up on the ground. Underwing moths get their name because they have brightly colored lower wings, which are normally hidden under the top wings as they rest during the day. When disturbed, they may open their wings to reveal the surprising colors to confuse predators. Most of their caterpillars rely on excellent camouflage to hide against bark, stones, or lichens. This particular species, though, has one more trick. If disturbed, it will flip violently back and forth until it turns upside down. To see the result of this maneuver, use your computer mouse to move the cursor on your screen over the caterpillar. This will disturb it sufficiently to evoke the typical reaction.