The scorpion is a nocturnal arthropod which feeds mainly on spiders and insects. It's tail usually curved upward and forward over the back and has a venomous stinger. The species of scorpions that live in Arizona cannot inject a sufficient quantity of venom to kill an adult human, though their sting can be quite painful. Many desert plants have barbs or thorns which can make hiking painfully inconvenient at times. The two types that you'll run into most often are cholla and cats claw acacia.
Cholla are a cactus which consists of thorny segments with barb hooked spines.
When brushed the segments break off and imbed themselves in your flesh. The spines are sharp enough to penetrate boot leather and seem to slide effortlessly into your skin. Some individuals carry a comb or tweezers to remove these segments, but the best solution is to simply watch where you're going. My personal nemesis is the cats claw acacia. The plant tends to grow across unused trails and is unavoidable in many cases.