The Mutant Bugs are shown in Plague. They are bugs that can grow to the size of minibuses. They have sharp "gnashing mandibles" and are nicknamed "Roaches" by the townsfolk. They are loyal to the Darkness who puts them under the control of Drake Merwin (undead version). Drake refers to them as his "army" and is seen to have ridden on one of them.
They are virtually unkillable, their weak spot being the underside of their body and their internal organs. They are fast, nimble, and have long black tongues in which they can reel in their prey. Sam Temple manages to jump inside a bug's mouth, snagging his foot on a mandible that cuts his leg. Inside the bug, Sam uses his powers to burn the bug's insides, killing it within minutes. Brianna also realizes that you can stab them on the underside of the body when Caine assists her by flipping them onto their backs in "The Bug Battle" of Perdido Beach.
They may be somewhat related to the Greenies, flying snakes that shoot green goo from their mouths. The green goo infects your body, slowly destroying you by hatching the bugs within your body. The victim can see signs of infection as small gnashing mouthparts (much like the Roaches mandibles) poke through the skin throughout the infection. The victim, however, cannot feel pain, There has been three known cases, Hunter, Roscoe and Dekka. Two out of the three die.
The Bugs, under command of Drake, attack Perdido Beach, resulting in the death of around 36 people. Many of the bugs are killed by Brianna and Caine. Drake and some of the bugs try to take Little Pete/Nemesis to the Darkness but Astrid throws Little Pete to the bugs, thinking that killing him will end the FAYZ. In panic, Little Pete makes the bugs disappear, then he too disappears, freeing himself of his body. The FAYZ wall, however, does not come down as Astrid predicted.