Arachnids with lobster-like pincers and tails bearing stingers. Scorpions have existed for a long time (the oldest known fossils are 400 million years old, and some early scorpions were much bigger than those of today - the fossilized Brontoscorpio and Gigantoscorpio are estimated to have been a metre long each in life). Scorpions possess a pair of feather-like forms under their stomachs which they use to 'feel' the ground for vibrations which could tell of nearby predators or prey. When mating, the male scorpion grasps the female by the pincers, deposits a 'package' of sperm onto the ground and then pulls the female over it, so she can lower herself and absorb it through an opening in her body. Despite their fearsome reputation, scorpions are not all dangerous. In fact many, like the Emperor Scorpions from West Africa and Black Forest Scorpions from Asia are harmless. A way of determining as to whether a scorpion may be dangerous is to look at its pincers. Harmless scorpions like Emperors and Black Forests have large strong pincers and relatively small tails. At the other end of the scale are the dreaded Fat-tail Scorpions, which have small, slender pincers and large muscular tails which can drive their deadly stingers through shoes. Scorpions exist in tropical, desert and scrubland environments.
Emperor Scorpions, Redclaw Scorpions, Black Forest Scorpions, Egyptian Gold Scorpions - all harmless, as I can assure you since I've kept them as pets in the past.
I'd just like to mention Spike, the grandmother of my family of Emperor Scorpions (now sadly all deceased). RIP Spike.