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.

Radscorpions
The normal radscorpions are the common sight in all the wasteland. These poisonous hunters can possess different speed, but they are always deadly in groups. In Chicago, their stings sometimes have a green, glowing radioactive aura. Sometimes, especially on the West Coast, young, small radscrorpions could be seen near their adult relatives.

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.

Albino Radscorpions
The Albino Radscorpion is a new enemy which is added to Fallout 3 in the Broken Steel DLC pack.

Glowing Radscorpions
These creatures are native to the radioactive crater near the town of Carbon. They managed to spread around the Texas and also could be found in the Secret Vault's lower, radioactive, mutant-infested levels. 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 are native to the crater near the town of Carbon, but have spread all around Texas. They also could be found in the Secret Vault's lower, radioactive levels. Much like the glowing radscorpions, they are the result of prolonged radiation exposure. 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. They are heavely irradiated, surpassing even glowing radscorpions.

Unique Giant Radscorpions
These creatures are rumored to live near irradiated crater of Carbon. High radiation levels of the crater caused them to mutate to enormous size and develop some traits uncommon to their kind. They are the biggest of all radscorpions, rivaling a big truck in size, have a pair of claws that they use as both weapons and shields, and a big reddish eye in the center of their head. Being fast and strong, they still have one known weakspot: the limbs on which their giant claws are. These limbs could be damaged and ripped off their body, leaving them to rely only on their tail.

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

Tactics

 * In Fallout 3, radscorpions are susceptible to quick melee weapons, such as the Shishkebab.  Keep the scorpion in front of you and you can either slash and move to its side and keep it turning while you kill it, or dart, slash and back up, timing it so you are backing up when it strikes. It only takes a couple of Shishkebab slashes to kill the normal size scorpions, and five to six to kill the giant ones (depending on your melee skill).
 * In Fallout 3, Radscorpions do not have a "weak spot" that can be targeted for extra damage (i.e. they have no "head" for headshots). This makes VATS combat and firearms less effective against them.
 * Radscorpions cannot turn very easily, so circling around it whilst firing is a good way of avoiding damage.
 * Also, in Fallout 3, a radscorpion will stop for just a second giving you the advantage to back away and attack them with a shotgun after and before the attack.
 * Presumably radscorpions hunt you by feeling vibrations through the ground. If you run from them and climb on a large rock they will suddenly stop and then retreat, leaving you to attack them with a ranged weapon or a grenade.

Related quests

 * Stop the Radscorpions