Screwworm larvae eat the living flesh of their hosts

Most blowfly larvae are nature's cleanup crew, feeding exclusively on decaying matter or dead tissue. The New World screwworm is a gruesome exception. This parasite targets living, warm-blooded animals, including livestock and occasionally humans. When a female fly finds even a tiny scratch on a host, she lays hundreds of eggs. Once they hatch, the larvae use specialized, hook-like mouthparts to drill into the healthy muscle, creating a deep pocket that looks as though a literal metal screw has been driven into the flesh.