I turned over a log in the woods last week and was pleased to see nearly two dozen pairs of bright red legs disappear beneath the leaves: a centipede. I immediately thought of three questions I have answered before about these intriguing creatures. Is a centipede bite dangerous? Is it true giant centipedes live in the Southwest? Does anything eat centipedes?

The short answers are, no, yes, yes. No, not all centipedes are dangerous. Yes, some southwestern U.S. and tropical centipedes are enormous, approaching a foot in length. A species in Venezuela is large enough to enter caves where they capture and kill bats. Yes, southeastern crowned snakes (which do not bite people) eat centipedes.

Despite their common name, a close look at centipedes quickly reveals that most have nowhere near a hundred legs, but they use the ones they have to glide over the ground like liquid mercury. Centipedes are noted for their venom, and some scientists suggest they are the oldest known lineage of venomous land animals. The morphological mechanism is relatively simple: a pair of hollow pincers connected to glands in the head region that produce highly complex venom. As with other venomous animals, such as snakes, spiders and scorpions, the biochemical makeup of the poison varies from species to species and has not been thoroughly analyzed.

Injecting a lethal dose of venom into another animal allows a centipede to capture its prey chemically rather than physically. They want nothing to do with humans and will try to escape if confronted. Attacking a human on purpose would be a fool’s errand as we are hundreds of times larger than any centipede. Bites can occur by accident (such as rolling onto one in a sleeping bag or stepping into a boot left on the ground). Human mortality from the venom per se has not been reported in the United States. But the bites certainly can be painful. I was bitten once (my fault, not the centipede’s) and was definitely aware of it. In addition to stinging, burning sensations around two reddish pinpoints on my index finger, a red streak appeared on the inside of my arm and began moving up. After about an hour the pain and red streak subsided. Unpleasant but not unbearable.

Centipedes, like most of the world’s flora and fauna, offer us a lesson: scientists have discovered only a tiny portion of the biological mysteries they hold. In 2020 a technically complex but fascinating study was published in the journal Science Advances. The group of researchers, led by neuroscientist Shilong Yang (Chinese Academy of Sciences), reported how centipedes use their venom in different ways, depending on what they are biting. If the victim is a prey item they intend to kill, they deliver one version of their venom. If the victim is another centipede the dose is different. Although the molecular basis is not entirely understood, the venom effect on members of its own species is different, causing a temporarily debilitating, but not lethal, reaction. Many questions remain about how centipedes use their venom in combat with each other.

Another lesson from centipedes is how all members of a taxonomic group can inherit a negative reputation because others in that group can hurt people. Eastern house centipedes are a poster child example of guilt by association. They are not just benign, they are beneficial. Anything making a living tracking down unsavory insects in the home has my vote. I like to call them fairy centipedes. These small whiteish creatures are about an inch or so long with 30 fluttery legs. The antennae are as long as the body. These centipedes look like a flickering movie reel as they scamper across the floor. I have picked them up many times and not been bitten, although they have small pincers and venom. My admonition to them when I put them back down on the floor is “go find yourself a roach to eat.” 

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