Invertebrates
Saddleback Caterpillar
Acharia stimulea · also called saddleback caterpillars
Resting on a garden leaf, a saddleback caterpillar displays its bold green saddle-shaped marking, a warning sign worth heeding given the venomous spines covering the rest of its body capable of delivering one of the most painful stings among North American caterpillars.
Overview
The saddleback caterpillar, Acharia stimulea, is a boldly marked, venomous larva native to forest, garden, and landscaped habitat across a broad range of the eastern United States. Its distinctive green saddle pattern, painfully stinging spines, and eventual transformation into a comparatively unremarkable adult moth make it one of the more visually striking and genuinely hazardous caterpillars encountered in eastern gardens and forests.
A warning pattern worth heeding
The saddleback caterpillar’s bold green-and-brown saddle marking is not just decorative, functioning as a clear visual warning that the venomous spines covering the rest of its body are best left untouched.
Status
Least Concern — widespread and common across suitable forest and garden habitat throughout the eastern United States.
Saddleback Caterpillar: common questions
Why does the saddleback caterpillar sting so badly?
This species is covered in venomous spines, particularly two prominent horn-like clusters at each end of the body, and contact with these spines delivers venom capable of causing immediate, intense pain along with localised swelling and redness, making it one of the more painfully stinging caterpillars found in North America.
How can you identify a saddleback caterpillar?
Look for a distinctive oval green marking resembling a saddle across the back, bordered by brown, a striking and fairly unmistakable pattern that also serves as a useful warning to avoid touching the venomous spines covering the rest of the caterpillar's body.
What does the saddleback caterpillar turn into as an adult?
This species eventually transforms into a comparatively plain, brownish adult moth, an appearance considerably less memorable and dramatic than the boldly marked, venomous caterpillar stage most people actually notice and remember.
What does the saddleback caterpillar eat?
This species feeds on the leaves of a wide variety of trees, shrubs, and garden plants, making it a fairly generalist feeder rather than one dependent on a single specific host plant, which contributes to it being commonly encountered across gardens and forest edges alike.