relative to the tip. Biology Most scorpion species are nocturnal or crepuscular, finding shelter during the day in burrows, cracks in rocks and tree bark. Many species dig a shelter underneath stones a few centimeters long. Some may use burrows made by other animals including spiders, reptiles and small mammals. Other species dig their own burrows which vary in complexity and depth. Hadrurus species dig burrows as over deep. Digging is done using the mouth parts, claws and legs. In several species, particularly of the family Buthidae, individuals may gather in the same shelter; bark scorpions may aggregate up to 30 individuals. In some species, families of females and young sometimes aggregate. Scorpions prefer areas where the temperature remains in the range of , but may survive temperatures from well below freezing to desert heat. Scorpions can withstand intense heat: Leiurus quinquestriatus, Scorpio maurus and Hadrurus arizonensis can live in temperatures of if they are sufficiently hydrated. Desert species must deal with the extreme changes in temperature from day to night or between seasons; Pectinibuthus birulai lives in a temperature range of . Scorpions that live outside deserts prefer lower temperatures. The ability to resist cold may be related to the increase in the sugar trehalose when the temperature drops. Some species hibernate. Scorpions appear to have resistance to ionizing radiation. This was discovered in the early 1960s when scorpions were found to be among the few animals to survive nuclear tests at Reggane, Algeria. Desert scorpions have several adaptations for water conservation. They excrete insoluble compounds such as xanthine, guanine, and uric acid, not requiring water for their removal from the body. Guanine is the main component and maximizes the amount of nitrogen excreted. A scorpion's cuticle holds in moisture via lipids and waxes from epidermal glands, and protects against ultraviolet radiation. Even when dehydrated, a scorpion can tolerate high osmotic pressure in its blood. Desert scorpions get most of their moisture from the food they eat but some can absorb water from the humid soil. Species that live in denser vegetation and in more moderate temperatures will drink water on plants and in puddles. A scorpion uses its stinger both for killing prey and defense. Some species make direct, quick strikes with their tails while others make slower, more circular strikes which can more easily return the stinger to a position where it can strike again. Leiurus quinquestriatus