The common house fly, Musca domestica, is typically associated with unsanitary locations like garbage, waste, and decaying organic matter, leading many people to be surprised when they find these insects congregating on their bright, healthy flowers. This behavior is a perfectly normal, biologically driven activity for the fly. A house fly’s life depends on finding simple, accessible energy sources, and flowers provide these necessary nutritional rewards. Understanding this insect’s basic biological needs and foraging habits explains why a beautiful blossom can be just as appealing as a compost pile.
Why Flowers Are Appealing to House Flies
House flies require simple carbohydrates to fuel their flight and daily activities, and flower nectar offers a readily available source of sugar. Nectar typically contains a mixture of simple sugars, such as glucose, fructose, and sucrose, which the flies can metabolize quickly for energy. The presence of other sugary substances, such as honeydew—a sweet, sticky excretion produced by sap-feeding insects like aphids that coats plant leaves—also serves as a potent attractant to foraging flies.
The insect’s location process relies heavily on both visual and olfactory cues. House flies are attracted to a wide range of volatile organic compounds, including floral scents that mimic the odor of fermentation or decay, which they associate with their primary food sources. Visually, house flies respond to certain color wavelengths and patterns, a trait exploited in commercial fly traps. Flies are generalist feeders, but they often prefer flowers with open structures and colors like white, which make the nectar visually accessible.
The Actual Activities of Flies on Plants
Once a house fly lands on a flower, its main objective is to feed using its sponging mouthparts, which are designed only for ingesting liquids. If the food source is a solid sugar, such as crystallized nectar or pollen grains, the fly must first liquefy it through external digestion. It accomplishes this by regurgitating saliva onto the solid material, dissolving the sugars into a consumable liquid that the fly then sponges up.
Another common behavior is “bubbling,” where the fly exudes a droplet of regurgitate from its mouth before re-ingesting it. This action helps eliminate excess water from the meal, concentrating the consumed nutrients. The plant surface also serves as a convenient site for resting, thermoregulation, and congregation, where flies may engage in mating behaviors. These visits inevitably result in the deposition of small, dark spots known as “fly specks,” which are the fly’s excreted wastes.
Assessing the Impact on Plants and Home
The impact of house flies on a healthy ornamental plant is minimal, as they do not consume the plant tissue itself. House flies are generalist feeders and are not considered effective pollinators, although they may passively transport pollen grains on their bodies as they move between blossoms. The primary concern associated with house flies on flowers is the potential for mechanical pathogen transfer.
House flies are known vectors for numerous disease-causing organisms because they frequently visit unsanitary materials, such as feces, compost, and garbage, picking up bacteria like Salmonella and E. coli. When the fly subsequently lands on a clean surface, it deposits these contaminants through its feet, regurgitation, and defecation. The presence of their waste is an aesthetic nuisance, especially on indoor plants or those near food preparation areas.
Effective Strategies for Deterrence and Removal
The most effective approach to managing house flies is to eliminate their primary breeding and feeding sources, which limits the overall population near the home. House flies breed in moist, decaying organic matter. Sanitation is the first line of defense, requiring regular removal of pet waste, ensuring garbage cans are clean and tightly sealed, and promptly disposing of grass clippings or spoiled food.
To deter flies directly from flowers, homeowners can use natural scents that house flies find repulsive. Planting certain herbs near affected plants serves as an effective, non-toxic repellent:
- Basil
- Mint
- Lavender
- Marigolds
Essential oils, such as eucalyptus, peppermint, and lemongrass, can be diluted in water and lightly sprayed on surrounding non-edible surfaces to create a scent barrier. For direct removal, non-toxic traps, such as a simple mixture of apple cider vinegar, sugar, and dish soap in a shallow container, will attract and trap flies away from the flowers.