A Chihuahuan desert arthropod that looks ferociously dangerous is the big, black, whip scorpion, or vinegaroon. Normally they’re found in rocky country, only after significant rain events.
In most towns in West Texas tan wind scorpions, or solifugids, with pincers on their face and long front legs that run very fast are often mistakenly called vinegaroons. Solifugids are great house guests, eliminating brown recluses, scorpions, and sometimes black widows that inadvertently enter a household.
Vinegaroons look ferocious! Most folks are unwilling to touch one, or to let one crawl on them. Captive vinegaroons eat crickets. When fed to a vinegaroon, the crickets run all about, but the big black predator appears unaware of them until one runs into its legs. The vinegaroon then blunders off in the cricket’s direction but the cricket usually escapes. The vinegaroon pursues, as if it is feeling vibrations, and if it catches up in a few minutes the vinegaroon tries to position the cricket between its big pincers or pedipalps . This scares the cricket into running towards the vinegaroon, who opens its huge claw-like pedipalps wide, which then fold in and hold the cricket against its face. CRUNCH!
If a person sticks a pencil in between the pedipalps, the strength of the big pincers can be evaluated. One would think it would grab it strongly, and pinch it hard enough to give a little tug, but it doesn’t. If the observer then touches the tail with the pencil, the tail vibrates quickly, but it must be agitated briskly for it to release acetic acid from the long whip tail. The spray is difficult to see, but the odor is a slap-in-your-face attention-getter. The acetic acid serves as a solvent that dissolves insect exoskeletons, yet the spray does not irritate human skin.
Normally vinegaroons are nocturnal. They burrow or hide under rocks, carrying their prey to their burrow. Like almost all aridland creatures they wait for rain and become active only on nights of high humidity. When foraging, they will sit and wait at different locations near their den, but sometimes do bump into food as they move. They’re well defended by acetic acid.
The acetic acid is contained in a pair of glands located on a mobile turret where the tail begins. The discharge is usually well-aimed. The highly concentrated acetic acid also contains minor amounts of a few other acids that also come from pygidial glands in their abdomen. It’s the highest concentration of acid found in any known chemical defensive secretion, having a concentration about 15 times that of vinegar.
Vinegaroons eat crickets, katydids, spiders, scorpions, solifugids and even blister beetles. Stink bugs and rainbugs (red velvet mites) are left alone. They have few predators. Rodents, lizards, and centipedes all rub their affected body part against the soil after being sprayed. The predatory grasshopper mice plow their mouth into the sand for several minutes after getting a mouthful of the spray. A vinegaroon can discharge up to 10 times before running out of ammunition.
Sometimes a vinegaroon loses its tail in a struggle with a predator, but the tail regenerates with the next molt if it’s immature. Mature adults don’t shed their exoskeleton. Immature individuals take 2-4 years to go through four molts, depending on available resources, and adults live 3-7 more years, reproducing annually. After a lengthy mating encounter of thirteen hours, females can have up to 70 eggs Up to 300 vinegaroons have been found on one acre in prime habitat, almost entirely unnoticed by the humans that live among them.
Nature Notes is sponsored by the Dixon Water Foundation and is produced by KRTS Marfa Public Radio in cooperation with the Sibley Nature Center in Midland, Texas. This episode was written by Burr Williams of the Sibley Nature Center.