Where Flies Go In Winter: Do They Hibernate Or Die?

by | Flies, Insects

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If you’re enjoying cooler weather with no flies buzzing around you or your home, you’re probably wondering where all the flies go for winter and why they suddenly return in spring.

In winter, flies hide in warm places before dying of old age within 4 weeks, but will die off sooner if the temperature drops below 32°F (0°C). Flies have adapted to the cold by slowing down their lifecycle: eggs laid in fall and winter hatch, but larvae take 2-3 months to become flies when it’s warmer.

Flies have found many ways for their species to survive even the coldest of winters, and they will always be back to annoy you as soon as the weather warms up. Knowing where flies go in winter will help you find them in different stages of their lifecycle and kill them before new flies emerge in spring.

Where flies go in winter

Flies find a warm place to live until they die of old age

House flies live for about 4 weeks, so flies that emerge in fall or winter time won’t live to see the end of winter. But they need to do something to make it through the cold until they die of old age.

Click here to find out how to identify house flies.

Photo of hundreds or house flies looking for somewhere to spend their winter
These flies are gathering together in a group before going to look for a warm place to hide for the winter.

To survive as long as they can in cold weather, flies:

  • Huddle together in groups and look for a warm place to hide together. When things rot or ferment, they give off heat, which flies love. This is why you will often find flies spending winter in garbage piles, compost bins, on anything that’s decomposing or rotting, and on any metal parts or containers holding warm decaying matter, such as bins
  • Crawl into crevices and cracks in the walls of houses for protection from the cold
  • Look for gaps in window or door frames to spend their winter
  • Seek shelter in sheds, barns, or chicken coops, where they lay eggs in animal manure
  • Hide in people’s houses where the temperature is controlled and there is food to eat (these flies usually live the longest as they have the best conditions)
  • Come out during the day to sit in the sun and warm up for as long as possible before going back to their hiding places

Flies go into a type of hibernation when it gets too cold

Flies that live in areas where the winters are very cold have found a way to go into a sort of hibernation that helps them live longer. Flies get very sluggish when it’s cold and stop moving, even though they are alive, if the temperature drops to 45°F (7°C).

A fly’s hibernation is called diapause, and there are a few signs that a fly is entering and has started diapause: As it gets colder, the fly starts crawling instead of flying while looking for somewhere safe to rest. As time passes, the fly stops moving altogether in a bid to save both energy and body heat.

Going into diapause helps the fly stay alive in cold temperatures that could otherwise kill it.

Any time the weather gets too cold for a fly to survive, it can go into diapause. This means that diapause doesn’t only happen in winter, but it could happen at any time of the year.

Once a fly enters diapause, it can stay in this still sleep for a few weeks. As soon as it gets warmer, the fly wakes up and carries on with fly life as though nothing ever happened.

Flies die when the weather gets too cold

We know that flies get lazy and motionless if they get cold enough at around 45°F (7°C). But if it gets colder than that and drops to 32°F (0°C) or below, most flies cannot survive and die off.

Flies do not build nests, store fat, or have fur coats to keep them warm in winter. But they have found ways to make sure that their offspring survive even the coldest of winters…

Flies slow down their lifecycle so young flies emerge in spring

Fly eggs continue to hatch in fall and winter, but the time it takes for the larvae to grow into flies is slowed down from a week in warm weather to 2+ months in winter. Fly larvae can survive cold weather better than flies, and a slower lifecycle makes sure larvae become flies when it’s warmer.

Here’s how flies do it…

Adult flies spend most of their day mating and laying eggs. When winter approaches, the females find a warm place near food where they lay hundreds of eggs over 3 days. The larvae that hatch from these eggs are called maggots, and they look a lot like worms.

Photo of maggots with a description of how they survive the winter
Photo of maggots.

If the female flies lay their eggs in a warm, moist spot, maggots hatch from the eggs within 20 hours. The maggots live off a nearby food source, which can be compost in a compost bin, garbage, animal manure, decaying leaves, rotting fruit, or anything else the maggots might enjoy.

When things rot or ferment, they release heat. This is why a compost bin or a garbage bin is always a few degrees warmer than the outside temperature. It’s this heat that keeps maggots warm in winter as they feed and move on to the next phase in their lifecycle: becoming pupae.

Before turning into pupae, maggots crawl up to 50 feet to find somewhere safe, warm and dark to hide. They often bury themselves up to 6 inches (15 cm) deep under the ground, in animal bedding, or in whatever pile of warm waste they are eating.

The pupa stage is when a maggot wraps itself in a hard case called a pupa, which acts much like a butterfly’s cocoon. The pupa can be brown, yellow, red or black. No matter the color, the pupa is tough and is there to protect the changing insect inside.

Photo of several fly pupae to show the color and shape of the shell as the shells protect the maggots from the cold to become fli
Photo of pupae.

Once a maggot is hidden and protected by the pupa, it grows legs, wings, and antennae. After a time, the insect comes out of its pupa as a young adult fly.

In warm weather, a maggot turns into a fly during the pupa stage within 2 to 6 days. But in cold weather, this transformation can take up to 27 days, which shows us how a fly’s lifecycle slows down in winter. This helps to keep the maggot safe in the pupa in bad weather and gives the fly a better chance of emerging in spring.

How to get rid of flies in winter

If you need to get rid of flies and maggots in winter, before spring arrives, you’ll find a list of the best tips and recommended products from Amazon to get the job done quickly:

  • Expose fly eggs and larvae: Before winter frosts arrive, go outside and turn over the top 6 inches (15 cm) of the soil in your flower beds, the compost in your compost bin, and any animal bedding or manure you have on your property. This will expose maggots and pupae, and they will quickly die in the cold.
  • Remove breeding areas: Clean up any garbage, mulch, dead animals, animal droppings, food, stagnant water, or anything else that might be attracting flies. Close any gaps or cracks in the walls or roof of your house or outbuilding where flies might be getting in or hiding.
  • Block their entry to your home: Stop flies from coming into your house to breed in winter with magnetic screen doors or magnetic screen windows.
  • Look for eggs, larvae, and flies in your home: Go through your home and inspect your walls inside and outside for cracks and crevices, your attic, your basement, your drains and gutters, as well as your window and door frames. See if you can find any eggs, larvae (maggots), pupae or flies.
  • Use the best methods to kill what you find:
  • Throw fly eggs, maggots and pupae into boiling water to kill them.
  • Keep one of these electric fly swatters nearby to kill flies, or leave these traps on to attract and catch annoying flying insects in your home.
  • Pour this gel drain cleaner into your floor drains, garbage disposal, sink drains, stormwater drains, and any other drains or pipes on your property. It will quickly kill fruit flies, drain flies, and sewer flies that are overwintering in there.
  • If flies or maggots are hiding out in a safe place that you can’t access, like carpets, baseboards, or cracks in the wall, it’s best to spray them with this home defense spray made with essential oils. It can be sprayed indoors and outdoors, from any angle, and it’s safe to use around children and pets. More good news is that it won’t stain anything you spray it on.

I'm Monique. I love gardening and spending time in my backyard growing things. Here's where I share what I know about backyard pests and what to do about them, so you can enjoy your yard too.

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Monique loves gardening and spending time in her backyard, where she grows flowers, succulents, herbs, fruits, and vegetables.

Monique spends a lot of time researching how to protect her backyard from harmful pests and trying to attract beneficial insects and animals.

She shares everything that she learns and tests here at Backyard Pests.


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