Two-Striped Walking Stick

Anisomorpha buprestoides — the two-striped walking stick (also called the 'devil rider', 'witches' horse', or 'mussbug') — is one of the most chemically defended walking sticks in NA Phasmatodea (the stick and leaf insects) and one of about 6 species in genus Anisomorpha. The species is widespread across the southeastern US (especially Florida, Georgia, the Carolinas, eastern Texas) where it is a familiar large arthropod of pine flatwood and hardwood forest habitats. Adults are 4-7 cm body length (females larger than males — the 'larger female' is responsible for the 'devil rider' name discussed below), with the species' diagnostic features: dark brown body marked by THREE PALE LONGITUDINAL STRIPES (despite the 'two-striped' common name — the central stripe is sometimes less prominent than the lateral stripes, leading to occasional 'two-striped' counting), short stout legs, and small body size compared to many other walking stick species. The species is unlike the more familiar slender twig-mimic walking sticks (e.g., the Northern walkingstick Diapheromera femorata — already in the Wild Files) — Anisomorpha is shorter and stouter, with less-effective twig camouflage. The species' major defensive feature is one of the most powerful CHEMICAL DEFENSES in NA Phasmatodea. Two-striped walking sticks have specialized PROTHORACIC GLANDS (located on the underside of the prothorax, just behind the head) that produce a TOXIC ALDEHYDE-BASED DEFENSIVE SECRETION called ANISOMORPHAL (a monoterpene aldehyde named after the genus). When threatened, the walking stick sprays the secretion in a precise jet that can be aimed accurately at predator threats UP TO 40 CM AWAY — the spray jet emerges from the prothoracic gland openings and is directed at the source of the threat through controlled body posture. The spray is INTENSELY IRRITATING to vertebrate eyes and mucous membranes — bird and small-mammal predators that are sprayed experience severe pain and immediate retreat, providing effective defense for the otherwise-vulnerable walking stick. Humans accidentally sprayed in the eyes can experience severe pain, temporary blindness lasting 10-30 minutes, and CORNEAL DAMAGE in some cases requiring medical treatment. The species is one of the most-cited examples of arthropod chemical-defense injuries to humans in southeastern US natural history. The species is also famous for the 'DEVIL RIDER' MATING BEHAVIOR — pairs of two-striped walking sticks are commonly found with the SMALLER MALE riding on the BACK OF THE LARGER FEMALE for extended periods (sometimes days at a time). The behavior is interpreted as MATE GUARDING — the male rides on the female to prevent rival males from displacing him, ensuring his sperm fertilizes the female's eggs. The 'devil rider' name comes from the visual impression of a small dark figure 'riding' a larger walking-stick body. Larvae feed on a variety of southeastern US shrubs and herbaceous plants. The species is harmless to humans EXCEPT for the chemical-defense risk — handling should be avoided, especially around the face and eyes.