A White-marked Tussock Moth (Orgyia leucostigma), one of the more festive of our caterpillars. They have a catholic diet, eating both evergreens and deciduous trees, a feat made possible by their robust gut chemistry.

The caterpillars not only use their hairs for defense (and advertisement of that defense), but use them to sense attacks and respond appropriately. The caterpillars drop to the ground if their hairs are jostled by a fast-moving object. They trundle away when the agitation is calmer. Thus they avoid common predators: Polistes wasps that pounce in an aerial attack, Sinea assassin bugs that launch ambushes from the leaf, and Podisus stink bugs that amble up and probe with mouthparts. Dropping is a good defense against the former two. Walking away is sufficient for the latter.

The adults are also interesting, but not nearly so bright. The female is wingless and emits a pheromone that the well-antennaed male follows upwind.

“Caterpillars” in The Forest Unseen has more on this species, including some reflections on how struggles with predators change the pattern of light in the forest. Well-haired caterpillars can afford to reveal their locations by shot-gunning leaves with holes. Undefended species are more tidy eaters. Spineless? Tidy your plate.