Flies are a common nuisance that can invade homes and bother people trying to enjoy the outdoors. Their presence often prompts the question – do flies go away when it’s dark? The answer isn’t quite so simple. While flies do exhibit some changes in behavior at night, they don’t completely disappear or stop being active in the darkness. Understanding fly behavior day and night requires looking at the unique biology and behavior of different fly species.
Do House Flies Go Away at Night?
The common house fly is one of the most prevalent fly species that invades homes. House flies are diurnal, meaning they are most active in daylight hours. The house fly sleeps at night and rests in dark places. However, they don’t completely disappear after dark.
House flies need warmth and will congregate inside homes and buildings at night to keep warm. During the day, house flies will forage for food and lay eggs. At night, they become less active but can still be seen flying around light sources looking for warmth and food. Their night time activities are reduced, but house flies will still be present after dark.
Nocturnal Fly Behavior
While house flies rest at night, some species of flies are nocturnal and become more active after dark. These include:
| Moth flies | Phorid flies |
| Drain flies | Owl midges |
Moth flies get their name because they resemble small moths when flying. They are attracted to lights and fly mostly at night, hiding in dark, damp spaces like sink drains during the day. Phorid flies thrive in filthy conditions and also fly at night to lay eggs on decaying material.
Drain flies live and breed in the gelatinous gunk that builds up in drains. They emerge at night from drain pipes to mate and look for food. Owl midges are tiny flies less than 1 mm long that fly low to the ground at night in huge swarms. They can be serious pests around outdoor lights and patios.
These nocturnal flies become more problematic at night because people turn on lights that attract them. Their nocturnal behavior brings them into homes through open doors or windows where interior lights lure them inside.
Circadian Rhythms in Flies
A big factor in flies’ day and night behavior is their circadian rhythms. Circadian rhythms are physical, mental, and behavioral changes that follow a 24 hour cycle in response to light and dark.
Flies have molecular clocks in their brains that synchronize their circadian rhythms to light and dark. During the day, the clock genes stimulate foraging activity, mating, and egg-laying. At night, they stimulate sleep and inactivity. Even in total darkness, this circadian clock allows a fly’s metabolism and behavior to follow a 24 hour cycle.
Disrupting this natural rhythm can affect fly behavior. Constant light exposure can create arrhythmic flies with irregular sleep-wake cycles. Red light at night has less of a disruptive effect on flies than white or blue light. This is because flies see red wavelengths poorly. The molecular clock drives innate behavior patterns optimal for survival in the flies’ niche.
Daytime Resting Spots
While less active at night, house flies and some diurnal species don’t disappear entirely. During daylight hours, flies rest in sheltered spots that provide safety from predators and temperature extremes.
Inside homes, flies congregate in attics, basements, cellars, and crawl spaces. Outdoors, flies hide in shrubbery, beneath leaves and rocks, inside holes in trees, and under the eaves of buildings. Cool, dark places provide refuge from the hot sun and predators like birds and spiders.
At night, flies emerge from these daytime shelters to seek food and warmth. Artificial lighting attracts them into homes at night if windows and doors are left open. Sealing all possible entrances helps prevent night time fly intrusions. Installing yellow bug lights also makes a home less attractive to flies at night.
Cooler Temperatures Make Flies Less Active
Flies are cold-blooded insects, meaning their body temperature and metabolism depends on ambient temperature. As temperatures drop at night, so does fly activity. Cooler weather makes flies more lethargic, causing them to rest instead of actively flying around.
However, flies don’t hibernate or go dormant in cold weather like bees or wasps. Lower temperatures just reduce their activity levels. Milder nights may still see flies buzzing around porch lights or hovering by windows. A sudden cold snap can slow down flies dramatically, but warmer weather will cause them to resume vigorous activity.
Overwintering Survival of Flies
While flies are less active in cold weather, they have adapted strategies to survive harsh winters in cooler climates. Different species have developed specialized overwintering behaviors.
The house fly overwinters in sheltered spots like attics, barns, and stables. They enter a chill coma state, with slowed metabolism to conserve energy. Cluster fly swarms invade attics and walls to hibernate in tight masses. Stable flies and deer flies overwinter as larvae buried underground. Other flies survive as pupae, larvae, or eggs hidden in leaf litter or other sheltered locations.
These overwintering flies take shelter in dark places and remain inactive until warm weather returns. Whilefly populations decline in winter, the hardiest individuals survive to restart the cycle in spring. So flies don’t completely disappear, even in the dead of winter.
Night Time Pest Control Targets Flies
Understanding fly behavior day and night helps target control methods when flies are most vulnerable:
– Use traps and insecticides outdoors at dawn and dusk when flies are most active.
– Seal entry points and use indoor traps at night when flies congregate on walls.
– Apply residual sprays to outdoor resting spots like shrubs and dumpsters.
– Treat overwintering sites like attics and basements in late fall/early winter.
– Install fly light traps and nets during summer nights to catch invading flies.
An IPM approach uses multiple tactics to control flies when they are active or resting, both day and night. Knowledge of fly biology provides an advantage in reducing populations when they are vulnerable.
Conclusion
While less active in the dark, flies do not completely disappear or go away at night. Their biology and circadian rhythms cause changes in behavior after daylight hours, but flies still seek food, warmth, and shelter in the darkness. Restlessness fly activity around lights shows they are still present at night, requiring control measures after dark for peak effectiveness. An integrated pest management plan targeting flies at all hours provides the best defense against these persistent pests.
