How Do Flies Sleep? Best Answer

How Do Flies Sleep? They don’t! Flies have evolved without the need for sleep. They can rest, but not in a way that we would consider sleep. Some little critters don’t play by the rules of nature, and flies are one of them.

Fly brains stay switched on for days at a time if left undisturbed. Once they are disturbed, they require a few minutes to hours of recovery time until they can start flying and hunting again.

Flies do not need sleep the way we do. They don’t require periods of unconsciousness to recover from daily wear and tear or restore their energy levels.

What Are Flies?

Flies are a large order of insects called Diptera. Flies have a single pair of wings that they use for flying and hovering, unlike other insects that can fly, such as moths or bees with two pairs of wings. Another defining feature is the small knob on their antennae, known as a “scape.”

Most flies eat plants or animals, which they locate using their exceptional eyesight. Flies mostly eat liquids; they can dip their beak into almost any source of liquid to extract the nutrients inside.


Flies are extremely robust insects that can survive for several weeks even without food or water. Some species will enter a state of suspended animation called diapause when conditions are unfavorable.

Flies reproduce very quickly, with some species laying up to 10 eggs a day. In warm weather, flies can complete the whole cycle from egg to adult in as little as two weeks.

Do Flies Sleep?

Flies do not sleep in the way that humans or other animals do. They have to stay constantly alert because being caught unaware by a predator could be fatal for them.

Flies are incredibly sensitive to movement, which they need to avoid to survive for long periods. Any sudden movement nearby will cause them to react quickly and fly away.

There are a few theories as to why flies do not sleep. One is that they don’t have the bodily functions to support periods of unconsciousness for extended amounts of time, such as the slowed heart rate or decreased body temperature than other animals experience when falling asleep.  

Another explanation is that they need so little sleep. They don’t need to rest to repair and build new tissues, so they don’t experience the same needs as other animals.

It’s also possible that flies have evolved beyond the need for sleep and spend most of their time resting with their eyes open to watch out for any potential predators or prey items.

How Do Flies Sleep?

Flies don’t sleep the way that humans or other animals do.

So if flies don’t sleep, then what do they do when they’re resting? They become sedentary and remain in one spot for an extended period. Many rests with their eyes closed, but their brain activity is still increased compared to when they are fully awake.

How Do Flies Sleep
How Do Flies Sleep

They may be taking advantage of their ability to enter a state of suspended animation called diapause. Flies will do this when food is scarce or it’s too cold outside to reproduce.

Diapause allows them to survive until conditions improve without expending energy on flight, reproduction, eating, or moving around.

Also Read: Do Spiders Sleep?

Where Do They Go at Night?

Flies will often sleep inside sheltered places where they feel safe and protected. They like to rest in dark locations because predators can find it difficult to see them against a dark backdrop.

Some flies prefer the indoors, hiding under furniture or behind curtains until nighttime falls when they become more active again. Some species are less likely to fly around at night, preferring to rest on walls or in nooks and crevices.

How many hours does a fly sleep?

In general, a fly can go without sleep for about four days. They need to sleep from time to time to restore their energy levels and be ready for another busy day of hunting or reproduction.

Some species will rest with their eyes open during the night, keeping watch or waiting for prey. Other flies prefer to sleep outside rather than risk being inside where they might contact a predator.

Do flies sleep with their eyes open?

There is some evidence that flies sleep with their eyes open, although it’s not clear whether this is because they keep watching for predators or because of the difficulties involved in closing and opening their wings.

Flies can’t afford to be caught napping when a predator comes along and try to avoid resting in dull locations where there isn’t much left to see.

Do Flies Sleep in the Dark?

Flies have a very different approach to light and darkness than humans, so it isn’t easy to understand their perspective.

Insects can’t see color or have depth perception, making them less likely to use nighttime to avoid predators. Instead, they’re more concerned with the direction in which the moon is rising to navigate their way around.

Flies are attracted to bright lights, so they sleep in dark areas but avoid resting underneath bright lights. It’s also likely that they don’t want to stay in one place for too long and prefer the safety of a moving target instead of a stationary one.  

The Bottom Line

Flies have a unique way of sleeping. They can sleep on the wing, so they are often seen flying past windows at night.

I hope this blog post answered your question about how flies sleep. If not, please let me know in the comment below, and I will do my best to answer it for you.

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