Originally an aquatic species, these bloodworms (order Glycera) steady migrated from the coastal waters of the Atlantic coast after mutating, and have made their homes in the dry and dusty wasteland. Despite a total change in habitat, bloodworms have retained two of their original traits. The first of these is their burrowing ability; instead of burrowing into wet sand and silt, their four hollow jaws have become adept at plowing through the tough and dried soil. They use this ability quite a bit, ambushing prey from beneath the surface, and then returning underground to catch their prey unaware again.
The other trait that they kept, alluded to by their style of hunting, is that they are obligate carnivores, requiring meat to survive. They are roughly 120 to 150 centimeters (four to five feet) long so they have no problem ambushing and taking down megafauna such as humans.
Bloodworms are often encountered in groups of two to four individuals and are tenacious predators, ambushing their prey, taking a bite out of it, and then returning underground to do the same over and over again. Even worse, whenever they pop out of the ground, they create a thick dust cloud that is impossible to see through, making them even harder to attack. Naturally, the larvae are much weaker than adult bloodworms, but while they still contribute to the swarm, they are deadly creatures.