Question
Hi, I Was Wondering If You Know if a Devil Hickory Horned Worm Is Poisonous and if it Bites.

Answer
The hickory horned devil is the largest caterpillar in the United States. Although it has a ferocious appearance, the hickory horned devil is harmless. This insect starts as a tiny caterpillar after hatching from one of hundreds of eggs laid by a regal moth. Over a matter of weeks, it grows and molts until it reaches its amazing mature size. Then the hickory horned devil crawls to the soil and digs to form a subterranean cell in which it molts into a pupal stage. The fall, winter and spring is spent as a pupa in the soil. Next summer, the insect molts into the adult stage that is an orange moth with gray edges and veins called the regal moth. Although the regal moth is fairly large, it is not as large as you would expect based on the size of the caterpillar. One reason that hickory horned devils are such a surprise to people is because they are actually somewhat rare. In spite of their large and forbidding appearance, birds are extraordinarily fond of them as food. Consequently, few of the hundreds of eggs laid by regal moths produce caterpillars that survive to produce offspring of their own. Because hickory horned devils are harmless to humans and are relatively rare, no control measures seem warranted.

It "bites" only the leaves it eats. The horn are there to try to scare away bird etc that feed on the caterpillar. It is harmless.