Most maggot species feed exclusively on dead tissue, but some species absolutely will eat living flesh. The answer depends entirely on which type of fly laid the eggs. This distinction matters whether you’re curious about a wound, worried about an infestation, or have heard about medical maggots used in hospitals.
Most Maggots Prefer Dead Tissue
The vast majority of fly larvae you’d encounter are necrophagous, meaning they feed on dead or decaying organic matter. Blowfly species like the common green bottle fly and the blue bottle fly breed in carrion and are naturally drawn to necrotic (dead) tissue rather than healthy, living cells. Their digestive secretions contain three groups of protein-dissolving enzymes that break down dead tissue effectively but don’t attack healthy cells in the same way.
This selectivity is what makes certain maggots useful in medicine. The green bottle fly (Lucilia sericata) is the species cleared by the FDA for wound care. When placed on a chronic wound, these larvae consume dead tissue while leaving healthy tissue intact. Their secretions actually stimulate the growth of new blood vessels and skin cells, pushing the wound from an inflamed state into an active healing phase.
Species That Attack Living Flesh
A smaller but significant group of fly species are obligate parasites of living tissue. The most notorious is the New World screwworm (Cochliomyia hominivorax). Unlike blowflies that wait for tissue to die, screwworm larvae are biologically designed to consume living flesh. Female screwworms lay eggs at the edges of even tiny wounds on warm-blooded animals, and the hatching larvae burrow inward using sharp mouth hooks that tear into healthy tissue.
The destruction is aggressive. As the larvae feed, wounds expand in both size and depth. Affected areas become painful, swollen, and may bleed or produce a foul smell. The larvae orient themselves head-down in the wound with their breathing apparatus at the surface. Left untreated, screwworm infestations can destroy oral, nasal, and eye tissue. The CDC classifies this species as causing obligate myiasis, meaning the larvae cannot complete their life cycle without feeding on a living host.
Another flesh-eating species, Wohlfahrtia magnifica, is found across the Mediterranean, the Near East, and parts of Central and Eastern Europe. A related species, W. vigil, occurs in the northern United States and Canada. Adult flies in these species lay eggs directly in or near wounds. The larvae feed inside the host for about a week and can migrate from just beneath the skin into deeper tissues, often causing extreme damage.
What a Maggot Infestation Looks Like
The medical term for a maggot infestation in living tissue is myiasis. People with myiasis typically develop a lump in the skin as the larva grows. In some types, larvae may shift position beneath the skin but generally stay localized rather than traveling throughout the body. More destructive species like screwworms create open, expanding wounds where the larvae are visible inside the tissue.
The type of myiasis depends on the fly species involved. Primary myiasis occurs when flies target healthy or minimally wounded tissue. Secondary or facultative myiasis happens when species that normally feed on dead tissue opportunistically infest a wound that has both dead and living tissue present. In these cases, larvae that typically eat only necrotic material may begin consuming living flesh at the wound margins if conditions allow.
How Medical Maggots Stay Safe
The maggots used in hospitals are a single species, raised in sterile laboratory conditions and disinfected before being applied to wounds. They’re classified as a medical device and used specifically for non-healing wounds like pressure ulcers, diabetic foot ulcers, and infected surgical wounds. Their secretions break down dead tissue, fight bacterial biofilms (the protective structures bacteria build on wound surfaces), and promote the growth of new, healthy tissue underneath.
Even with a species known to prefer dead tissue, medical maggot therapy isn’t appropriate for every situation. It’s not used on wounds near large blood vessels, in patients with severe bleeding disorders, or on wounds that penetrate into body cavities because the larvae can’t be safely retrieved afterward. Wounds near the airway are also off-limits. The therapy requires patient consent and cooperation, since the larvae need to be contained within the wound area and removed after treatment.
Why the Distinction Matters
Whether maggots eat live flesh is not a yes-or-no question. It’s a species-specific one. Of the roughly 150,000 known fly species, only a small fraction produce larvae capable of parasitizing living tissue. The green bottle fly maggot you might find on roadkill has no interest in your healthy skin. A screwworm fly, on the other hand, evolved specifically to exploit living hosts.
Geography plays a role in your risk. The New World screwworm was eradicated from the United States through a decades-long sterile male release program but still exists in parts of South America and the Caribbean. Wohlfahrtia species are limited to specific regions in Europe, the Middle East, and northern North America. If you’re in a tropical or subtropical area and notice a wound that seems to be growing rather than healing, with visible larvae inside, that warrants urgent medical attention since the tissue destruction accelerates as larvae grow.