Radscorpion

Radscorpions are an extremely large version of the North American Emperor scorpion, mutated by radiation. Contrary to some expectations, their poison grew more potent, not diluted. They are nocturnal and sensitive to light. Samples of poison from their tail can be used to make antidotes. Apart from their size, they look pretty much like normal scorpions, with shell color ranging from red to black.

Glowing radscorpions
Similar to normal radscorpions, glowing radscorpions are a bit more ferocious and much more radioactive. They're so radioactive that they glow (naturally). That means that just getting near these creatures will cause you some damage, and their claws will cause damage by radiation as well as their tail stinger.

Spitting radscorpions
Spitting Radscorpions are a step sideways on the evolutionary ladder from normal radscorpions. They have developed the ability to spit radioactive venom at distant targets. As a result, their claws are severely under-developed, used only for protecting the spitting radscorpion's head. Spitting Radscorpions are usually yellow in color with a bright red coloring on their back and legs.

Appearances in Fallout games
Radscorpions can be encountered in all Fallout games.