Radscorpion

Radscorpions are an extremely large version of the Emperor scorpion, which was prolific in pet stores at the time of the bombing, mutated by radiation. Contrary to some expectations, their poison grew more potent, not diluted. They are nocturnal and sensitive to light, however on the East Coast this is not the case, as giant and regular size radscorpions have been spotted in the daytime. Samples of poison from their tails 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.

Giant RadScorpions
Simply a much larger Radscorpion with a highly poisonous stinger that will deal 40 damage every 5 seconds. 4 Radscorpion Poison Gland are found upon death, as opposed to the usual one. They have no known weak spots, so be prepared for a fight. (I have noticed that all radscorpions seem to take more damage when you target their front claws, although it may be a fluke)

Giant Radscorpions often travel and fight in pairs. It's not uncommon to see one turn from the player, and back off, only to be joined by another and charge in, again. In fact, they seem to operate together often, only preferring to attack alone when their partner is dead.

Energy weapons and regular projectile weapons seem to have very little effect due to the Giant Radscorpion's tough outer shell. On the other hand, explosives and advanced melee weapons (such as the Shishkebab and the Super Sledge) are surprisingly effective. The only downside is that you have to get into close combat, where Giant Radscorpions are the most dangerous, but if you go backwards while attacking, you may get no damage from them..

They also seem to be less susceptible to the effects crippled legs. They are very fast for their size, and even with their legs crippled, they can catch up to the player very quickly. One effective strategy against Giant Radscorpions is to find a boulder or tree to run around while dispensing mines. Another strategy is to use a Missile Launcher at a distance to soften them up (one or two missiles should do) and then finish them off with an energy or plasma based weapon.

It has been reported that Giant Radscorpions do appear more often at higher levels. Fast traveling to some places including Regulator HQ trigger Giant Radscorpion respawns right outside the base. If the animal friend perk is activated, it may be noticed on higher levels that regular Radscorpions and Giant Radscorpions are more commonly found than Yao Guai. This effect may be attributed to the fact that insectile creatures are immune to this perk.

Note: This may be a bug I've seen occurances where a Giant Radscorpian was fighting a swarm of Worker Ants and was in-turn friendly towords me, I was skeptical at first thinking it just hadn't seen me butIi did indeed walk right infront of it.(I can second that one, it happened right in front of robot repair center). I also encountered a friendly Giant Radscorpian after it got into a fight with two wasteland scavengers and a enclave eyebot. This should be considered a random encounter, as it has also happened to me and does not seem to be a bug. I've encountered a friendly giant radscorpion KX-B8-11 Relay Tower before (more than once) which could also be a random encounter of types (on further inspection, the giant radscorpion turns hostile after the player hangs around for too long).

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.

Related quests

 * Stop the Radscorpions

Bugs

 * When the Animal Friend perk is activated, the Giant Radscorpions are not hostile anymore and will not attack you. Star Paladin Cross kills them, even when they aren't hostile.

I have a single rank of the Animal Friend perk (and I'm running the PS3 version of the game) and have never encountered this bug.