Walking sticks aren’t very cool unless they’ve got a sword or a blowgun hidden in them. Fortunately, Mother Nature provided us with her own vision of walkingsticks, insects capable of ejecting a noxious chemical spray with astonishing accuracy, blinding its victims. Now that’s cool.

Anisomorpha buprestoides by Mary Keim (CC BY-NC-SA 2.0)

Anisomorpha buprestoides is the common walkingstick native to the southeastern United States but also goes by the more metal names Devil’s riding horse, prairie alligator, and witch’s horse. How we got those names is beyond me. Walkingsticks are about 2.5 inches long – with females much larger than males – and no one is going to confuse one for an alligator. And a horse? Nothing is riding a walkingstick except for…well…another walkingstick…during…ummm…mating season. But we’re not going there, this is a family-friendly blog.*** Most walkingsticks are informally identified by their color or markings: white, brown, one-striped, white-striped, orange two-striped. It’s much easier this way.

*** We have Mr. Miller, the twins English teacher to thank for this. In order to pacify the raucous mob that poses as students, he tells them to Google their parents. Why would anyone do this? So the girls and their friends found the blog and think it’s hilarious. Now that 6th graders are a key demographic, I’ve probably got to watch the language a bit. Don’t be hard on Mr. Miller though, he’s an awesome teacher.

When frightened the walkingstick emits a chemical spray from its thorax, resembling a fine spray of milky fluid. Walkingsticks have the ability to not only aim the spray in nearly any direction but eject from either one or both secretory glands that house the toxin. Intended targets are the usual predators, like birds, reptiles, and spiders, but if push comes to shove they won’t hesitate to fire upon larger targets.

Mossimo the Chihuahua finally decided to pick on someone his own size. He spotted a funny looking bug in his backyard and chose to put his nose where it didn’t belong. The walkingstick, doing what walkingsticks do, sprayed him in the eye. Mossimo yelped, jumped backward, and ran away crying. He really was crying, his left eye immediately swelled and started to tear. His owner gave him some doggy-grade anti-inflammatory drugs and he seemed better. The next morning, however, his owner – obviously a Jimmy Hendrix fan – noticed a “purplish haze” in the eye and rushed him to the vet. There was a corneal ulceration in Mossimo’s eye, as well as miosis and blepharospasm – a constriction of the pupil and closure of the eyelid. Little Mossimo recovered just fine and he’s off doing whatever chihuahuas do – probably yipping and biting at peoples’ ankles. (1)

Humans make good targets, too. An 8-year-old boy – not related to Mossimo – came across a walkingstick on a bush in his backyard. When he was about 1 foot away the insect sprayed a red fluid towards his face, causing immediate pain in his eye. Despite flushing the eye with a ton of water he still had a lot of pain and blurred vision, so his parent brought him to the ED. He had damage to his cornea and continued pain for a week, but recovered just fine. He’s now off doing what 8-year-olds do – annoying his parents, being a slob, and not flushing the toilet (OK, those are my kids). (2)

The chemicals involved in the defensive toxic spray is a mixture of terpene isomers, with the most abundant being anisomorphal (3, 4). Components and relative ratios of the secretions change with the maturity of the walkingstick but all are irritating to humans, and once described as “molten lead.”

While Mother Nature’s walkingstick may not hold a hidden sword, it is a sharpshooter, so be wary. If you are in the American southeast and see a stick move…stay far away, don’t be a Mossimo.

References:

1. Brutlag, Ahna G., Lynn R. Hovda, and Michael A. Della Ripa. “Corneal Ulceration in a Dog following Exposure to the Defensive Spray of a Walkingstick Insect (Anisomorpha Spp.).” Journal of Veterinary Emergency and Critical Care 21.4 (2011): 382-86.
2. Paysse, Evelyn A., Samantha Holder, and David K. Coats. “Ocular Injury from the Venom of the Southern Walkingstick.” Ophthalmology 108.1 (2001): 190-91.
3. Dossey, Aaron T., Spencer S. Walse, and Arthur S. Edison. “Developmental and Geographical Variation in the Chemical Defense of the Walkingstick Insect Anisomorpha Buprestoides.” Journal of Chemical Ecology 34.5 (2008): 584-90.
4. Meinwald, J., M.s. Chadha, J.j. Hurst, and I. Eisner. “Defense Mechanisms of Arthropods – IX Anisomorphal, the Secretion of a Phasmid Insect.” Tetrahedron Letters 3.1 (1962): 29-33.

** Homepage image of Anisomorpha buprestoides by Mary Keim (CC BY-NC-SA-2.0) **

Anisomorpha buprestoides by Mary Keim (CC BY-NC-SA-2.0)