Did That Twig Just Move? How to Identify a Walking Stick Insect

It is one of the great small surprises of a late-summer evening: you notice a thin brown twig resting on the wall, the porch light, or the leaf of a shrub — and then it lifts a leg and takes a slow step. What looked like a piece of the plant is a walking stick, an insect that has spent millions of years evolving into a near-perfect imitation of a twig. From late July through August the largest adults appear, and that is exactly when people do a double take and wonder what on earth they are looking at.

How to Identify a Walking Stick

Walking sticks (also called stick insects or stick bugs) are built entirely around the twig disguise, and a few features give them away once you look closely:

• A long, extremely slender body — the common northern walkingstick runs about 3 to 4 inches as an adult, thin as a pencil lead
• Color that ranges from green to brown, often matching the plant it is sitting on
• Six long, thread-thin legs and a pair of long antennae, all held stretched out to blur the outline
• Very slow, deliberate movement, often with a gentle back-and-forth sway that mimics a twig moving in a breeze
• No wings in most North American species, so it walks or clings rather than flies

The camouflage is so good that most people only spot a walking stick when it moves or when it turns up somewhere unnatural, like a wall or a window screen. During the day they often hold perfectly still, and they are easiest to find at night around lights.

Are Walking Sticks Harmful?

For most of the country, no. The common walking sticks of the northern and central United States do not bite or sting, carry no venom, and are completely harmless to people and pets. They are plant-eaters, munching the leaves of oak, hazelnut, and other hardwoods, and they rarely occur in large enough numbers to damage a tree. Handling one gently is fine — just be careful, because their legs are fragile and can break off.

There is one regional exception worth knowing. In the Southeast, the two-striped walkingstick (sometimes called the "devil rider" or "musk mare") can spray a defensive chemical from glands behind its head when threatened. It is aimed at a predator's face, and if it reaches human eyes it causes intense burning and temporary irritation. If you are in the Deep South and find a pair of stout, striped walking sticks, admire them from a step back and keep them away from your face — do not lean in close or provoke them.

A Few Things That Make Them Remarkable

• Many species can reproduce without a mate, with females laying fertile eggs on their own
• The eggs are dropped to the ground one at a time and look startlingly like tiny seeds, complete with a nutritious cap that ants carry underground
• A walking stick that loses a leg can often regrow it at the next molt
• Despite the twig act, they are not related to twigs at all — they are insects in their own order, Phasmatodea, meaning "phantom"

When You Want to Be Sure

Between the harmless northern walkingstick, the chemical-spraying southern species, and the occasional leaf-mimic katydid that gets lumped in with them, it helps to know exactly what is clinging to your screen door. Snap a photo and Spotter will identify the insect and tell you whether it is a harmless twig-mimic or one of the few you should give some space.