The fusion of a human and ant. Human element allows these monsters to reproduce individually, but ant instincts drive feral Formicrawl to form colonies where only a single female is permitted to breed, as determined through physical combat once per year. If others of her kind are unavailable to challenge, a lone female Formicrawl defaults to the Queen mindset and can make a very difficult monster to care for, viewing every creature around her as a lowly worker.

Formicrawl are able to squirt a volatile acid from a gland between their rearmost legs, and may actually explode when severely injured.