The order Phasmatodea includes insects commonly known as walking sticks or stick insects. These creatures are masters of disguise, blending into the foliage of gardens and forests, which often leads to surprising encounters. Due to their size and unusual appearance, many people wonder if walking sticks pose a threat, specifically whether they are capable of biting or stinging a person.
Identification and Behavior
Walking sticks are plant-eaters, feeding exclusively on the leaves of trees and shrubs. Their body structure is designed for mimicry, closely resembling the twigs or branches of their host plants. In North America, species range in length from about two to eight inches, with long, slender bodies and legs contributing to their camouflage.
Camouflage is their primary defense against predators. When disturbed, they may sway their bodies slightly to imitate a twig moving in the wind. They also use reflex immobility, dropping to the ground and playing dead. Walking sticks are slow-moving and generally nocturnal, which helps them avoid detection.
The Simple Answer: Biting and Stinging
Walking sticks do not possess a stinger or any venom apparatus like bees or wasps. They are physically incapable of stinging a person. Their mouthparts consist of mandibles designed solely for chewing and grinding plant matter, making biting a large animal an ineffective defense. Although a large specimen might attempt a minor pinch if roughly handled, this action is rare and causes no meaningful harm to human skin. The concern about their danger comes not from a bite or a sting, but from a different, less common defense strategy.
Chemical Defense Mechanisms
While most walking sticks rely on camouflage and immobility, some species employ a more active defense: a chemical spray. The two-striped walking stick (Anisomorpha buprestoides), found primarily in the southeastern United States, is the most well-known example of this behavior. When this insect feels threatened or is handled, it can accurately spray a noxious liquid from a pair of glands located behind its head, called prothoracic glands.
This defensive secretion is a strong-smelling, irritating chemical compound, often a type of terpenoid, which acts as a contact repellent. The spray can be painful if it contacts sensitive areas, such as the eyes or mucous membranes. Exposure can cause immediate burning sensations, temporary blindness, and chemical conjunctivitis.
If exposure occurs, the most important action is to immediately and thoroughly rinse the affected area, especially the eyes, with copious amounts of clean water for 10 to 15 minutes. Although the effects are usually short-lived, it is advisable to seek medical attention for eye exposure to prevent further complication. This chemical discharge is the sole potential hazard associated with walking sticks.