If you’ve got a really curious kid at home (or are the curious type yourself), then you must have heard this question: where do flies go in the winter? It might sound like a funny question but it’s very valid. All summer you see them almost everywhere, annoying your pets, getting on your nerves, and making a nuisance of themselves. But then winter comes and you can’t see them anymore.
Everyone knows that bears hibernate in the winter. So, why is so little known about this infamous pest? Do flies hibernate during the winter? Or do they call a meeting to strategize on how to infuriate the human race even further?
Today, we have dug deep to find the answer to this question and are excited to share it with you. So, without further ado, let’s find out where flies go in the winter.
Flies: An Overview
During our research, the first answer we got to this was, “To the glass foundry to be turned to bluebottles!” Okay…maybe we got that from a site with jokes for kids. But that was just to lighten the mood a little. Now, let’s really get to business.
The truth is that although most of us use the word “fly” to describe houseflies, bluebottles, and the like, there are actually over a million different species of flies. Of those one million species, only about a tenth of them have been scientifically described (around 125,000).
So, there are literally thousands of different flies swarming around your house right now. You’ll probably only notice the larger ones because they’re more obvious and more visible. The same thing happens in the winter, too. A lot of flies remain active all year round. So, even though you don’t see them, there are still flies that are active in the winter. We’ll discuss where the rest go later on.
First, though, we’ll look at the life cycle of flies. This should help us gain some insight into how they can survive the winter.
Life Cycle of a Fly
It might seem hard to believe with their omnipresence and unswattability, but flies aren’t immortal. In fact, adult flies only live about 15–30 days. But, with their short lifespans, why do they seem to never reduce in population? The answer is that they have a very high reproduction rate.
The typical fly lives to do only three things: find food, breed, and die. There are no grand ambitions here. Life’s short.
On average, a female fly lays from 75–150 eggs at a time. In her lifetime, a female fly will lay roughly 500 eggs. That’s means each female fly in your yard can lay 500 eggs in just a month. Now you see why your yard never lacks flies.
Because flies are disgusting creatures, they’ll usually seek out the filthiest locations to lay their eggs when winter approaches. They’ll search for places like garbage bins, fecal matter, and the like to lay their eggs in. Other species may also lay their eggs in the soil, on developing fruit, or even on leaves.
These eggs will develop into the next stage: maggots. The maggot (or larval) stage is when they feed voraciously. At this stage, flies usually resemble plump, well-fed worms whose morphological characteristics vary depending on the species. For instance, some may have legs while others might not. Some may be smooth while others are spiny or hairy. They can be white, brown, yellow, or green.
One thing is for sure, however. They come with mouthparts that can chew on fruit and foliage. Not many changes occur at this stage, apart from their size, which might increase.
From the maggot stage, the potential fly enters the pupal stage. At this stage, the fly becomes dormant. It doesn’t feed or even move. It will often form a cocoon that covers it completely. Unlike the larva stage, a lot of profound changes occur at the pupal stage. It’s while in the cocoon that they change into the adult insects we all know and hate. They do this by developing wings, antennae, and legs.
After spending just 7–10 days in the previous stages, the fly is finally an adult. This is the most active period in a fly’s life and where it fulfills its last two ambitions: breeding and dying.
Flies In Winter
One fly species of whose whereabouts during winter we are certain are cluster flies. That’s because we often see them in our attics or other lonely rooms. You can recognize them thanks to their hairy thoraxes and stocky, grayish appearance. In winter, they don’t seem to be very active, though. We’ll explain this shortly.
Most scientists believe that flies have a sub-tropic origin. They most likely evolved in the Middle East and then spread to other parts of the globe alongside man. This would suggest that flies don’t have what it takes to survive the harsh winter conditions in other non-tropical regions of the world. So, what do they do?
Migration is one method that most flies use to escape the winter. Like the Monarch butterfly, many insects fly long distances between seasons. Other insects migrate from the southern states to the northern states in spring. The most obvious flies who use this maneuver are crop pests.
Overwinter as Larvae
Another method flies use to survive the weather is to pass the entire season in the immature larval stage. By hiding beneath a protective layer of fallen leaves, many insects can survive the winter. Some other insects are so smart that in the winter, they replace all water in their bodies with glycerol. And guess what? Glycerol is actually a form of antifreeze! Other larvae escape the winter by digging and making their home deep in the soil.
Overwinter as Nymphs
For stoneflies, dragonflies, mayflies, and similar flies, their nymphs live in streams and ponds beneath the ice all through the winter. There, they feed and grow until winter has passed, emerging in the spring as full-grown flies ready to torment us.
Overwinter as Eggs
Very few insects can lay eggs that can survive the winter. Some notable insects in this category are corn rootworms and praying mantises.
Overwinter as Pupae
Examples of insects that employ this strategy include Saturniidae moths and moths from the silkworm family. Their pupae are often found attached to branches of food plants during the winter.
This is when the metabolic activity in flies is drastically reduced. In fact, it’s kept just high enough to keep the flies alive and nothing more. At this stage, all activity, growth, and development are suspended and won’t resume until winter is over. This is what explains the semi-dormant behavior of those annoying cluster flies we talked about earlier.
So, now you know all the places flies go during the winter!