Desert Hairy Scorpion, Hadrurus arizonensis
Desert Hairy Scorpion, Hadrurus arizonensis. Scorpion collected within a residential community in the Buenas Aires area of Los Barriles, Baja California Sur, January 2018. Length: 12 cm (4.7 inches). Collection courtesy of Kyle Rousseau, Maple Ridge, British Columbia, Canada. Photograph courtesy of Eunice Rousseau, Maple Ridge, British Columbia, Canada.
Desert Hairy Scorpion, Hadrurus arizonensis. Scorpion collected in a residential property in Ivins, Utah. Photograph and identification courtesy of Bob Hillis, Ivins, Utah.
The Desert Hairy Scorpion, Hadrurus arizonensis, is a member of the Caraboctonidae family of Hairy Scorpions. The Caraboctonidae family consists of twenty-five members placed in two genera. Globally, there are eight species and two subspecies in the Hadrurus genus. The Desert Hairy Scopion is known in Mexico as Escorpión Peludo Del Desierto.
Desert Hairy Scorpions are tan to olive-green in color with yellow pedipalps, legs, and tail. The dorsal surface of their carapace and tergum are dark brown in color, and their tergum is separated into seven overlapping tergites. Their legs and tail are covered in small, dark brown hairs, which they are named after. These hairs detect vibrations in the air and soil, helping them locate prey and avoid predators. Slight sexual dimorphism is displayed with females typically having wider, stockier bodies while males tend to have larger pincers. The Desert Hairy Scorpion is the largest scorpion in North America, being between 10 cm (4 inches) and 18 cm (7 inches) in length and weighing between 4 grams and 7 grams.
Like most scorpions, Desert Hairy Scorpions mate in a multi-step process. When two receptive scorpions encounter one another, the male indicates his presence by rocking back and forth. The male then grabs the female by her side, clubbing her abdomen with his stinger. The male may inflict up to fourteen “sexual stings” on the back of the female. He then grabs the female by the pedipalps, leading her on a coordinated dance involving simple movements of back and forth rocking, until they find a suitable substrate on which to mate. Once their “promenade” is complete, the male deposits a spermatophore on the substrate and pulls the female over it, causing the sperm to be released into her gonophore and thus completing fertilization. Upon termination of the mating process, the male may club the female again before releasing his grip and returning to the wild. Females are not always receptive to mating and will often resist the male after he deposits the spermatophore to avoid accepting the sperm into her abdomen. Occasionally, after mating, the female may track down her mate and eat him. Desert Hairy Scorpions mate opportunistically at night. Mating can occur at any time of the year as long as conditions are humid and warm. Gestation is 6 to 12 months long and females are oviparous, giving birth to a large litter of 25 to 35 young. Their young, called scorplings, are small, white, and vulnerable at birth. Scorplings immediately crawl onto their mother’s back where they are carried for 3 weeks, until they have molted at least once and can live independently. This helps their young regulate temperature and moisture levels, as they have not yet fully developed an epicuticle to do so independently. They Hairy Scorpions typically molt 4 to 6 times before reaching adulthood at four years of age. Desert Hairy Scorpions have lifespans of seven to ten years in the wild and between fifteen and twenty years in captivity.
Desert Hairy Scorpions are nocturnal and spend most of their time in burrows or under rocks, avoiding the sweltering heat of the day. They become dormant during the winter as temperatures drop, often living underground in burrows or in caves. They are solitary and rarely territorial. However, they will attack and defend themselves when they are provoked by raising their legs, orienting themselves vertically, and striking blindly at anything deemed threatening. Desert Hairy Scorpions are carnivorous and often prey upon organisms of comparable size. Their diet includes insects and other invertebrates, lizards, small mammals, and other scorpions. They will often wait inside of a burrow and ambush prey with their stinger once the prey is in range. Additionally, they use their modified front pedipalps to grab prey. Compared to most scorpions, their venom is fairly weak. Their venom successfully immobilizes small insects and invertebrates, while having little effect on vertebrates such as lizards and small mammals. In turn, Desert Scorpions are primarily preyed upon by large lizards and owls. They are also preyed upon by other scorpions, both for food and to assert dominance.
The Desert Hairy Scorpion may be confused with the Stripe-tailed Scorpion, Paravaejovis spinigerus (smaller in size, ranging between 5 cm (2.0 inches) and 7.6 cm (3.0 inches) in length; tails that are thicker than their hands and pedipalps with brownish-tan stripes).
From a conservation perspective, the Desert Hairy Scorpion has not been formally evaluated. This species is not protected by the U.S Endangered Species Act or the CITIES international treaty. While their venom is not strong enough to be fatal to a human, EXTREME CAUTION should be used if encountered. Their stings are painful, often compared to a bee sting, and cause localized swelling. Individuals who are allergic to scorpion venom or who have compromised immune systems may experience more severe reactions, and medical attention should be sought in these cases.