What Do Gnats Eat?

Fruit Fly Diet

Fruit fly adults and larvae feed on the same things; the eggs and pupae do not feed. This list of preferred food sources includes:

  • Fruits
  • Vegetables
  • Organic matter in a stage of fermentation and decomposition
  • Slime produced by moist, organic matter that accumulates in poorly maintained drains, garbage containers, garbage disposals and other sources of waste products.

Moth Fly Diet

Moth fly larvae feed on the surface film of poorly maintained drains and pipes dirty waste disposal containers, plus places where sewer leaks occur. Adults of many moth flies may feed on nectar from plants and polluted water sites. Eggs and pupae do not feed.

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What Do Phorid Flies Eat?

Phorid fly larvae eat organic matter found in their developmental sites. Such sites include:

  • Rotting plants
  • Moist manure
  • Decaying animal carcasses
  • The slime that occurs on drains and waste receptacles
Phorid fly pupae do not feed. An interesting and perhaps very important management technique under investigation involves adult phorid fly females in the genus Pseudacteon. These female flies are known to deposit their eggs in the thorax of fire ants. When the fly’s egg stage is complete, larval phorid flies move to the head of the fire ant and begin feeding on the tissues in the ant’s head. After completely consuming the ant’s brain, the ant becomes a “zombie” and wanders about purposelessly until its head falls off and the fly pupates in the separated head, soon after developing into a mature adult fly.

Larval Feeding

Fungus gnat larvae feed on plant roots, other organic matter and fungi found in the soil. Fungus gnat pupae do not feed and the adult stage generally feeds on flower nectar. Larval stage feeding can sometimes damage plants and stunt their growth.