Invertebrates
Hag Moth
Phobetron pithecium · also called hag moths, monkey slug
Clinging to a leaf in an eastern forest, a hag moth caterpillar looks more like a scrap of windblown debris than an insect, its curling, hair-like projections hiding a handful of venomous ones among the many harmless strands covering its body.
Overview
The hag moth, Phobetron pithecium, is an unusually shaped caterpillar native to forest habitat across a broad range of the eastern United States, with an adult moth stage that looks entirely different from its larval form. Its bizarre, debris-mimicking caterpillar appearance, hidden venomous hairs among harmless-looking projections, and wasp-or-spider-mimicking adult form make it one of the strangest and most easily overlooked caterpillars found in eastern forests.
A caterpillar in disguise as something else entirely
Rather than looking like a caterpillar at all, the hag moth larva’s tangle of curling projections does a convincing impression of dead leaves or drifting fur, a disguise that hides its sting until it is too late to avoid.
Status
Least Concern — widespread and common across suitable forest habitat throughout the eastern United States.
Hag Moth: common questions
Why does the hag moth caterpillar look so strange?
This species' caterpillar is covered in curling, hair-like projections of varying lengths that give it an appearance closely resembling a tuft of dead leaves, fur, or debris rather than a typical caterpillar, an unusual camouflage strategy that has also earned the species the alternate common name monkey slug.
Is the hag moth caterpillar dangerous to touch?
Yes, several of its hair-like projections contain venom capable of causing a stinging, irritating reaction on contact, and because these venomous projections look similar to the many harmless ones covering the rest of the body, it can be difficult to tell which parts are actually dangerous before an accidental sting occurs.
What does the adult hag moth look like?
The adult stage of this species has a fuzzy, dark body and holds its legs and wings in a posture that can resemble a spider or wasp at rest, a strikingly different appearance from the caterpillar stage and a possible form of mimicry that may help the adult moth avoid predators.
Do all hag moth caterpillars look the same?
No, this species' caterpillars can vary noticeably in the exact arrangement, length, and colour of their hair-like projections between individuals, meaning no two caterpillars necessarily look identical even though they share the same general unusual, debris-like body form.