An arthropod of the class Arachnida and order Scorpionida. It varies in length from less than 2 in (5 cm) for the small bark scorpions of Arizona to 8 in (20 cm) for some African scorpions. Most scorpions are nocturnal and reclusive and are most active when the night temperatures remain above 70°F (21°C). The tail of the scorpion contains two venom glands connected to the tip of the stinger.