**Lesser House Flies** (*Fannia canicularis*) are common synanthropic flies (associated with human structures) often confused with the common House Fly. They are primarily a nuisance pest in poultry, dairy, and livestock facilities, where the larvae (maggots) develop in moist, decaying organic matter, especially poultry manure. They are characterized by a distinct, erratic flight pattern, rapidly flying back and forth in the middle of a room, which can be an annoyance in homes.
Taxonomy and Classification
Lesser House Flies belong to the order Diptera (flies). They undergo complete metamorphosis. Unlike the common House Fly, whose larva is a simple maggot, the Lesser House Fly larva is distinctly flattened and covered with fleshy, spine-like filaments, giving it a somewhat spiky appearance. They thrive in wet, liquefied manure environments that are too moist for the Common House Fly.
Physical Description
Adult Lesser House Flies are $1/8$ to $1/4$ inch long, slightly smaller than the common House Fly.
- **Appearance (Key ID):** Dark gray or black, with a slender abdomen (more slender than the Common House Fly). The male has a characteristic **erratic, circling, or hovering flight** pattern, often flying low beneath light fixtures.
- **Larvae:** Flattened, spiky, grayish-brown maggots found in liquid manure and decaying organic matter.
- **Conflict:** Primarily a nuisance pest, but they can mechanically transmit pathogens from manure to food or surfaces.
Distribution and Habitat
Lesser House Flies are found globally. Their main breeding habitat is moist, liquefied manure, particularly in poultry houses (deep pit systems) and pig farms. In homes, they are often an indicator of a sanitation issue or a nearby breeding source (e.g., an overflowing drain, compost pile, or pet waste area).
Behavior and Conflict
The conflict is high nuisance levels and mechanical disease transmission.
- **Nuisance:** Their continuous, erratic flying indoors is highly annoying.
- **High Density:** They can reach extremely high numbers in large animal production facilities, causing stress to livestock and workers.
- **Disease Vector:** They can passively pick up and transfer pathogens (bacteria, viruses) from the contaminated breeding site to food or human surfaces.
Management and Prevention
Control is integrated pest management (IPM), focusing heavily on sanitation and source reduction.
- **Source Elimination:** The primary control method is to eliminate the moist breeding material (manure, decaying food). In poultry operations, this means improving manure management to dry out the waste.
- Repair leaks and eliminate any standing water or excessively damp organic debris.
- Release beneficial parasitic wasps (e.g., *Muscidifurax* species) in livestock facilities to parasitize the pupae.
- Use residual insecticides on resting surfaces outside the immediate manure area.
- **Larvicides** can be applied to the breeding material, but sanitation remains the foundation of control.
Conservation and Research
Lesser House Flies are managed as high-priority sanitation and veterinary pests. Research focuses on improving integrated fly control programs in animal agriculture, understanding insecticide resistance, and refining biological control strategies using parasitic wasps.