Flies are common during warmer months. Their numbers reduce as seasons change. This article explores the seasonal patterns of fly activity and the environmental factors that drive these changes.
Seasonal Decline of Common Flies
The population of common flies, such as house flies, decreases significantly with the transition from summer to autumn. As temperatures consistently drop and the days shorten, their activity diminishes. This decline is a general pattern observed across many temperate regions.
While adult house flies have a relatively short lifespan, the overall population reduction during fall is due to more than individual deaths. Breeding activity begins to decline in October as the air cools.
Environmental Triggers for Disappearance
Several environmental factors contribute to the disappearance of flies. Decreasing temperatures are a primary influence, as flies are cold-blooded, relying on external heat for body temperature regulation. When temperatures fall below approximately 45°F (7°C), their bodily functions begin to slow. Lower temperatures also negatively affect their longevity and reproduction.
Shorter daylight hours, or photoperiod, play a significant role. As days become shorter in late summer and autumn, it signals winter’s approach, influencing their behavior and physiology. This change in light cycles can trigger a state of dormancy in some species. Reduced availability of food sources, such as decaying organic matter and animal waste, also limits their survival as seasons progress.
Regional Variations and Specific Species
The timing of fly disappearance is not uniform across all geographical locations. In warmer climates, some fly species may remain active throughout the winter, continuing to breed and forage. Homeowners in these regions might still encounter fly infestations during winter months.
Certain species, like cluster flies, exhibit distinct overwintering behaviors. As daylight shortens in late summer, adult cluster flies seek dry, sheltered areas, often entering buildings through cracks around windows or soffits. They then aggregate in wall voids or attics, entering a dormant state. Other flies, such as blue bottle flies and black blow flies, also use homes for winter shelter.
What Happens to Flies in Colder Months
When colder temperatures arrive, the fate of flies varies by species and environmental conditions. Most adult flies die when outdoor temperatures plummet, particularly with the first hard frost. However, many species survive the winter in immature stages, such as eggs, larvae (maggots), or pupae, which can remain dormant in protected environments like soil or leaf piles.
Some adult flies, like cluster and house flies, can enter a state of dormancy called diapause. During diapause, their metabolic activity is significantly reduced, conserving energy to withstand harsh conditions. These flies seek sheltered locations, including leaf litter, tree holes, or indoors in attics and wall voids, to survive until spring. They may also produce a natural antifreeze in their bodies to sustain freezing temperatures.