Fly death fungus

Description

Entomophthora muscae is a common zygote fungus that attacks and kills adult flies. It occurs worldwide in the Tropical and Temperate Zones. It occurs in the United States and southern Canada east of the Great Plains and on the West Coast, with few scattered records between.

Entomophthora muscae attacks flies in the families Muscidae, Calliphoridae, Sarcophagidae, Tachinidae, Drosophilidae, Scatophagidae, Culicidae and Syrphidae. Outbreaks typically occur in the spring and fall, when cooler temperatures and humid conditions are most suitable for spread of the fungal spores.

A fly is infected when a single airborne spore lands on it. When the spore germinates, the fungus penetrates the fly’s cuticle, and fungal threads (hyphae) spread throughout the body. As the fungus grows, the abdomen becomes distended, exposing the membranous portion on the abdomen and giving the fly a striped appearance. The fungus also attacks the fly’s brain and controls its behavior. It causes the fly to crawl to an elevated position, often to the tip of a stem, flower, or leaf, and attach itself with its tube-like mouthparts (proboscis). The hyphae secrete a glue-like substance that firmly holds the body in place.

The fly dies five to seven days after becoming infected. The dead fly has its wings spread outward, the legs stretched out, and the body angled away from the surface. This is an ideal position for the spores to be spread widely. About three hours after the fly’s death, the hyphae force cracks in the areas between the segments. It produces numerous, large, spore-bearing structures (conidiophores), each one with a single spore (conidium). This gives the abdomen a fluffy appearance.

A smaller, secondary conidiophore is often developed at the tip of a primary conidiophore. When it matures, within about three hours, it forcibly ejects conidia into the surrounding area, resulting in a “conidial shower.” When this happens on a window, the result is a large “halo” around the dead fly.

Male flies often try to mate with the corpse of a dead infected female, picking up spores in the process.

Similar Species

Entomophthora syrphi attacks only hover flies (family Syrphidae).

Habitat and Hosts

Flies in the families Muscidae, Calliphoridae, Sarcophagidae, Tachinidae, Drosophilidae, Scatophagidae, Culicidae and Syrphidae

Ecology

Season

Year round