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Did you know there is a group of caterpillars called "Slug Moth" Caterpillars? At first glance, you might mistake this tiny creature for a miniature slug rather than a caterpillar—and that's exactly what makes slug caterpillars so fascinating. Members of the slug moth family (Limacodidae) have evolved a body unlike almost any other butterfly or moth larva.

Instead of the familiar rows of fleshy prolegs that most caterpillars use for walking, slug caterpillars have greatly reduced legs and tiny suction-like pads on their underside. They glide smoothly across leaves on a thin layer of liquefied silk, moving in gentle rolling waves rather than taking individual steps. Their flattened, oval bodies and hidden heads give them an almost alien appearance.One species you may encounter is the Yellow-collared Slug Moth (Apoda y-inversum). Its bright green, slug-like caterpillar feeds on the leaves of hardwood trees, including oak, hickory, beech, and ironwood. Rather than chewing holes through the middle of leaves, it often creates neat, straight-edged bites along the leaf margins. Its head remains tucked beneath a protective fleshy hood while feeding, helping shield this vulnerable body part from predators. ***(Photo is on the right side)Another Wisconsin species is the Yellow-shouldered Slug Moth (Lithacodes fasciola). Its caterpillar is a flattened, oval-shaped bright yellow-green with narrow yellow and green stripes running the length of its body. Tiny crater-like pits dot its back, giving it a textured appearance. Like its relatives, it glides instead of crawls and feeds on a wide variety of deciduous trees and shrubs, including oak, maple, birch, cherry, apple, willow, beech, blueberry, chestnut, hickory, honey locust, hornbeam, and linden. ***Photo is on the left side)When fully grown, slug caterpillars spin remarkably tough, cup-shaped cocoons with a built-in circular escape hatch. The adult moths that emerge are small, fuzzy insects, often beautifully patterned in shades of brown, cream, and black.While some slug caterpillar species possess stinging spines capable of causing painful reactions, these two species are considered harmless or only mildly irritating. Even so, it's always best to admire caterpillars with your eyes rather than your hands.These unusual caterpillars are a wonderful reminder that nature is full of surprises. Even among familiar insects like moths, evolution has produced incredible diversity in form, movement, and survival strategies.Photo on the left is a green caterpillar with spiky texture rests on a leaf on a wooden surface. Wehr Nature Center logo is in the lower left corner.Photo on the right is a close-up of a green caterpillar with yellow lines running parallel to the body accented by tiny blue dots, perched on a leaf, showcasing its detailed texture and color. Wehr Nature Center logo is in the lower left corner. … See MoreSee Less