Bugs. Creepy crawlies. Beasties. Those little critters with exoskeletons- otherwise known as arthropods. The group that includes insects, like bumblebees and cockroaches, arachnids, like spiders and scorpions, and myriapods, like centipedes and millipedes.
Most bugs are little. Even the ones we think of as being big, like tarantulas or luna moths, are pretty little compared to us and most animals. So if you’re a bug, one thing you have to worry about is that there are probably big animals out there who want to catch you and eat you for lunch. To address this problem several bugs have evolved a lot of really clever ways to stay safe from all those big, hungry animals. Some bugs can run really fast, some are camouflaged, and some have painful stingers. And then there are bugs that have truly unique forms of self-defense.
One bug that has evolved a distinctive way of protecting itself is a vinegaroon, or whip scorpion. Vinegaroons are arachnids, which means they have eight legs, two body parts and no antennae. They look quite similar to true scorpions, except they’re missing the thick tail with the stinger at the end, and they’re missing the scorpion’s venom that’s in that stinger. Instead, vinegaroons have a flagellum (a thin whip-like appendage – but from this point on we’ll just call it a tail) that they use as a feeler because they don’t have very good eyesight.
Vinegaroons have a gland in their abdomens that produces a solution that is mainly acetic acid. Acetic acid is the same acid that’s in vinegar. That’s right – vinegar. When a vinegaroon feels alarmed or threatened by the presence of a predator, it secretes some of this solution from the base of its tail.
Now, you may think of vinegar as a tasty ingredient in Italian salad dressing and dill pickles. But in the wild, animals don’t eat salad dressing or dill pickles, and when an animal gets a spray of vinegar in its face, it doesn’t like it very much. It doesn’t like the smell, it doesn’t like the taste, and it doesn’t like the burning that results if the acid gets in its eyes. And if the predator is another arthropod, it doesn’t like the feel of the acid seeping through its exoskeleton. So it may just decide to leave the vinegaroon alone and go in search of more appetizing prey. That little spray of acetic acid is a very effective evolved deterrent against danger.
So if you’re ever walking around on a summer night in the southwest United States or Mexico and come across a vinegaroon, and you suddenly smell vinegar, you’ll know the critter isn’t happy about meeting you. But, don’t take it personally. To the vinegaroon, you’re just another huge, hungry animal.
by Sarah Rollin Naughton
Arachnid, Arthropod & Reptile Specialist: Outreach Educator, Philadelphia Zoo
Environmental Educator, Churchville Nature Center