Scorpions are small creatures with a crablike appearance, four pairs of legs, a pair of pincers and a long, segmented tail that curls up with a stinger on the end Their sting can be quite painful and have medical complications, with only rarely fatal effect for humans.
Most of the scorpions in the U.S. are found in the southwest, in the warm, dry climates of Arizona, California and New Mexico.
Scorpions are predatory, using their venom to subdue their prey and for defense.
Scorpions feature a chitinous exoskeleton and a segmented body to which their four pairs of jointed legs are attached. Thus, scientists place them in the phylum Arthropoda and the class Arachnida, which includes spiders, mites, ticks and harvestmen. There are over 1,500 species within the order Scorpiones. The United States is host to more than 70 of those species..
The scorpion’s body is composed of the prosoma, containing the carapace, chelicera and pedipalps; the central body part, called the mesosoma, containing the adbominal segments (tergites) where its legs are attached; and the metasoma, the segmented erectile tail. The scorpion’s tail culminates in the telson, where the stinger is located.
The three most common scorpions found in the Southwest are the Arizona hairy scorpion – Hadrurus arizonesis, bark scorpion – Centruroides exilicauda and te stripe-tailed scorpion, also known as the devil scorpion) – Vaejovis spinigerus.
The Arizona hairy scorpion ranges from Southern California, Arizona and is an intimdating five to seven inches in length, though its venom is not very potent as far as humans are concerned. Nevertheless, for those who have an allergic reaction to a sting, they can be very dangerous. They are yellow in color with darker coloring on top of body and have small brown hairs covering their bodies.
The bark scorpion ranges from Arizona to Southeastern California, Southwestern New Mexico, and Baja California and Sonora in Mexico.
These scorpions are venomous and dangerous to people, with the most potentvenom of any scorpion in North America. They are light brown in color and rarely more than three inches in length with a thin tail about 1/16 of an inch wide.
The stripe-tailed or devil scorpion likewise ranges from Southern California to Arizona and is venomous but not considered dangerous to most humans. It is 2.5 inches in length, of a light brown color with brownish stripes on the upper side.
The carapace usually supports a pair of median eyes at the top center. Two to five pairs of lateral eyes are found at the front corners of the carapace, though a few cave and mountain forest litter-dwelling scorpions are eyeless. Chelicerae, the scorpion’s mouthparts, and a pair of pedipalps, or claws used for prey capture and mating complete the head anatomy. The pedipalps are covered with trichobothria, sensory setae, that sense air-borne vibrations.
The mesosoma, protected by bony armour, contains the lungs, digestive organs and sexual organs, as well as bearing 4 pairs of walking legs and the pectines. The tips of the legs have small organs that detect vibrations in the ground. The pectines are feathery sensory organs which hang beneath the abdomen and trail on the ground. They are coated by chemosensors that provide detection of minute chemical signals that are thought to alert the scorpions to the approach of prey and also to be of use in mating behavior. The respiratory structure, known as “book lungs,” are spiracles that open into the scorpion’s body. The surfaces of the legs, pedipalps, and body are also covered with thicker hairs that are sensitive to direct touch.
The metasoma curves up and ends in the telson, which bears the bulbous vesicle containing the venom glands and a sharp, curved aculeus which delivers the venom.
Most species of scorpions reach adulthood at a length of between 2 and 3 inches.The longest scorpion in the world is probably the African Scorpion (Hadogenes troglodytes) which grows to over 8 inches in length. In the U.S., members of the genus Hadrurus (giant desert hairy scorpions) are probably the largest, growing typically to a length of about 5 inches, though sometimes longer.
. Scorpions are nocturnal and hide during the day. Some scorpions species will hide under rocks, logs and in cracks, other species will dig and hide in burrows.
Scorpions often ambush their prey, lying in wait as they sense its approach. They consume all types of insects, spiders, centipedes and other scorpions. Larger scorpions may feed on vertebrates, such as smaller lizards, snakes, and mice if they are able to subdue them. They capture their prey with their pedipalps, paralyzing them with their venom. The immobilized prey is then subjected to an acid spray that dissolves the tissues, allowing the scorpion to suck up the remains.
The pedipalps are used in scorpion courtship behavior. The male performs a kind of dance with the female, grabbing her pedipalps with his own and dragging her across the ground until he locates a preferred place to deposit his spermatophore, which is then drawn up into the female’s genital pore, near the front on the underside of her abdomen. Some species’ courtships include a sexual sting of the female by the male.Scorpion
Scorpion gestation periods vary from several months to a year and a half, depending on the species. Each brood will consist of about 24-35 young. They are viviparious – the young develop as embryos in the female’s ovariuterus. The young scorpions are born two at at time, climbing onto their mother’s back to be carried there until their first molt in about two weeks, when they will be large and strong enough to take care of themselves.
Scorpions do not metamorphasize as they grow, changing only in size and sometimes to a deeper color with each molt. Typically five or six molts over two to six years are required for the scorpion to reach maturity. The molting is accomplished by a split in the outer covering through which the scorpion must crawl in order to grow.
As well as being predators, scorpions are also prey. Many types of creatures, such as centipedes, tarantulas, insectivorous lizards, birds (especially owls), and mammals, including shrews, grasshopper mice, and bats hunt scorpions for food.
The pedipalps are used in scorpion courtship behavior. The male performs a kind of dance with the female, grabbing her pedipalps with his own and dragging her across the ground until he locates a preferred place to deposit his spermatophore, which is then drawn up into the female’s genital pore, near the front on the underside of her abdomen. Some species’ courtships include a sexual sting of the female by the male.Scorpion
Scorpion gestation periods vary from several months to a year and a half, depending on the species. Each brood will consist of about 24-35 young. They are viviparious – the young develop as embryos in the female’s ovariuterus. The young scorpions are born two at at time, climbing onto their mother’s back to be carried there until their first molt in about two weeks, when they will be large and strong enough to take care of themselves.
Scorpions do not metamorphasize as they grow, changing only in size and sometimes to a deeper color with the five or six molts over two to six years as the scorpion reaches maturity. Molting comes by way of a split in the outer covering through which the scorpion must crawl in order to grow.
Scorpion lifespans range from three to five years, though some species are thought to live 10-15 years. Some scorpions show sophisticated social behaviors, such as colonial burrowing and living in familial groups that share food.
Scorpion venom is used to subdue prey and to defend against threats, as well as in the mating process. The composition and action of the venom, consisting of mixtures of salts, small molecules, peptides, and proteins, varies as peptides are specialized and act as a neurotoxin which depolarizes the nervous system of the victim.
Scorpions regulate the delivery of the venom in scale to the size of their target. Some scorpions produce a transparent prevenom in addition to the more potent opaque toxin-rich venom. This enables the scorpion to conserve the venom for use when it is needed most, for larger predators or prey.
Text and photos from desertusa.com, courtesy of Jim F. Bremner.