Radroach

Great American cockroaches, colloquially called radroaches or simply giant cockroaches, are giant versions of the pre-war species that have been mutated by atomic radiation.

General characteristics
Found mainly in underground areas and sewers across North America, these creatures can usually be found in fairly large groups. They feed on the dead, but will go after living creatures if isolated. Their numbers are their biggest advantage. Radroaches live mostly in the areas east of California.

It is said that radroach innards are actually useful in the treatment of radiation poisoning, and are widely used by tribals for that purpose.

Capital Wasteland
Radroaches in the Capital Wasteland look similar to real-life cockroaches. Radroaches were enlarged extensively by mutation; to the point that they are as large as housecats.

Radroaches are not normally aggressive if you keep your distance. They will attack, however, if the player seems to threaten them, either by having a weapon drawn, invading their territory, battling another enemy nearby (which is limited to less than a foot around the creature), or attacking them directly. Generally, they will spread their wings in warning when they're about to attack.

Companions will attack them even when they don't attack or provoke the player as they show up as hostiles on the compass. However, they are very weak and do minimal damage, only posing a threat to a low level or low health player. They are much more numerous in the Capital Wasteland than they are in other regions like California or Nevada.

There are two named radroaches in Fallout 3: Fluffy and Jitters.

Fallout 3 features a unique Unarmed V.A.T.S. animation when killing radroaches: It is a boot stomp followed by a victorious boot grind.

Midwest
In the Midwest, radroaches are a common sight in the Wasteland. As in the Capital Wasteland, they can be encountered nearly everywhere, from old buildings to plains. However, they are drastically different and more dangerous than those met in the Capital Wasteland. They have a big, protected main body and small legs, and their saliva is incredibly toxic. They are very aggressive and attack every human unlucky enough to encounter them.

The Midwestern radroaches are more varied than their Capital Wasteland cousins. Three variations are known:

Small radroach
The weakest of the radroaches, they can easily be killed. However, their bites can poison an opponent, and when they are in large groups, they can kill even a prepared combatant. Small radroaches are nearly the same size as their relatives in the Capital Wasteland.

Large radroach
Similar to their smaller cousins, they are, however, larger (being approximately the same weight as a human) and have an ability to spit their toxic saliva.

Roachor
Roachor is a unique mutant radroach encountered by the Warrior of Midwestern Brotherhood of Steel. He is an "advanced" version of a large radroach, who lived in the Peoria facility. It appears Roachor was affected by the high amount of radiation coming from a strange production device which was used in manufacturing fusion batteries. He is even bigger than any large radroach, being the same size as a car, his body glowing with a greenish radioactivity. His poison is even deadlier than that of Midwestern radroaches.

Appearances
Radroaches appear in Fallout 3, Fallout: New Vegas and Fallout Tactics, and were to appear in Van Buren. They were also mentioned in Fallout Bible 1.

Behind the scenes

 * Their inclusion in the Fallout series is probably a nod to the common myth that cockroaches can easily survive a nuclear apocalypse.
 * In real life, roaches are noted for their relatively high resistance to radiation--about five to ten times that of humans. However, there are other insects and arachnids even more resistant to radiation, including fruit flies and scorpions. Their resistance to radiation can be explained through their cell-cycle. A tissue-cell is most vulnerable to radiation when it divides, but the cells of a cockroach only divides once every time it molts.
 * The radroach's G.E.C.K. id is AdamsMorganRoach. Adams Morgan is a district of Washington DC.
 * They appear in Fallout: New Vegas just before entering Primm from Goodsprings near a Irradiated pool, but they do not appear anywhere else in the game, apart from in the Sierra Madre in the Dead Money add-on. The fact that they are in the game suggets that the devleopers were possibley going to put more of them throughout the game, but for some reasons never did. Like in Fallout 3 they are friendly and only become hostile when attacked. One of the Radroaches was attacked by a Gecko suggesting they are hostile to each other, or at least Geckos are hostile to Radroaches.

Bugs

 * Sometimes Radroaches will be marked as allies and will not attack you or your Companions. However, switching locations will cause them to be marked as enemies, and they will attack as usual.
 * Rarely, when you kill a Radroach its torso will grow to abnormal size.

Gallery
Радтаракан