Arachnophobes, this one’s for you. Scorpions, vinegaroons, and sun spiders are arachnids which means they have eight legs, simple eyes, pincers, and two main body parts: the abdomen and the cephalothorax (a fusion of head and thorax). Vinegaroons and sun spiders also have powerful jaws. You may see all three in or around your house if you live in southern Arizona.
Scorpions have been around for about 400 million years. There are over 1,700 described species of which 30 species live in Arizona. The stripe-tailed scorpion is the most common in Arizona, followed by the bark scorpion, and the giant hairy scorpion. Both bark and stripe-tailed are two to three inches long. The giant hairy scorpion is up to six inches long.
Scorpions are nocturnal and diurnal. They feed upon insects, spiders, centipedes, and other scorpions. The larger scorpions go after small lizards, snakes, and rodents. In turn, they are preyed upon by owls, lizards, snakes, rodents, and bats.
Scorpion mating is a dangerous game because either one may eat the other. Mating does not involve primary copulation. Rather the male deposits a sperm packet on the ground and engages in an elaborate “dance” with the female to maneuver her over the packet. She then takes it up and may store it internally for months. She gives live birth and the newly hatched young ride on mom’s back until their first molt.
In Arizona, only the bark scorpion has venom potentially life-threatening to humans. About 25 other species throughout the world have dangerous venom. The sting comes from the tip of the tail (the telson). The sting of a bark scorpion is about as painful as that of a bee or wasp. Symptoms of envenomation include numbness, frothing at the mouth, difficulties in breathing (including respiratory paralysis), muscle twitching, and convulsions. Deaths are rare (unless you are allergic to the venom). There is an antivenom available.
The bark scorpion is the only one in Arizona that prefers to climb and it can cling to the underside of objects (like a piece of bark, a rock, a shoe, a piece of clothing, or a ceiling). In the house, they may get trapped in a sink or bathtub, or hide in dark areas of a closet. Outside, they may be in any loose pile of debris. The bark scorpion is the only one tolerant of others of its kind, so may live in large groups, especially in winter.
Scorpions contain a substance in their exoskeleton that makes it impermeable. It also causes scorpions to fluoresce under ultraviolet light. If you take a black light out on a summer night, you might be amazed at how many scorpions are around.
Vinegaroons are also known as whip scorpions. There are both tailed and tailless varieties. Although they may look formidable, they lack venom and are harmless. They do, however, have the ability to spray you, from an opening near the tail, with acetic acid (vinegar), and a solvent that attacks the exoskeleton of insects. You can handle them (see here). They are usually three to four inches long and black to dark brown.
They have four pairs of legs, but the front pair of legs are modified to act as feelers. These front legs resemble whips and are covered with many fine hairs. Vinegaroons feed mainly upon insects.
These animals occur throughout southeastern Arizona and Sonora, usually at higher elevations. They may be found under rocks, tree bark, or in debris. Like scorpions, the young ride on mom’s back (see here).
Sun spiders are not spiders but Solpugids (or solifugae). They are also known as wind scorpions. They lack venom and are harmless. However, they have formidable jaws. They are usually one to three inches long, yellow to tan, and very hairy. They are also very fast, voracious predators. Like the vinegaroons, the front pair of legs are used as feelers.
Sun spiders prey upon insects, other arachnids, and small vertebrates, including lizards. Sun spiders are nocturnal, and good diggers. They spend most of their time underground. They are most active in Arizona during the spring and summer. I occasionally find one in my house. I generally leave them alone because they will hunt down insects, spiders, and scorpions.
Mating involves a “dance” and stroking. The male will turn the female over and deposit sperm, which the female can store for later fertilization. She will dig a burrow and deposit up to 100 eggs, but does not care for them.
See also: Why do scorpions glow under UV light?