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What happens to a fly when it goes out the window?

When a fly goes out an open window, several things can happen depending on factors like the type of fly, how high up the window is, and weather conditions outside. Flies have small lightweight bodies and wings that allow them to navigate through the air with ease. However, strong air currents or wind speeds can overpower their ability to fly steadily. Going out a window exposes a fly to outdoor elements like wind, rain, and temperature changes that it is not adapted to handle. The fly’s fate depends largely on how far it falls and where it lands after getting pushed out the window.

What types of flies commonly go out windows?

The most common flies that end up accidentally flying out of windows are houseflies and bottle/drain flies.

Houseflies are attracted to food scraps and garbage inside a home. They can slip through small cracks around windows and doors to get inside. Due to their attraction to light, houseflies tend to congregate around sunny windows. A sudden breeze or draft from opening a window can catch their wings and carry them outside.

Bottle/drain flies emerge from breeding sites in drains or moist organic material. They are tiny (only 2-3 mm long) and often end up clustering around windows as they are drawn to natural light. Due to their tiny size, they can easily be blown out by a light breeze or wind gust near an open window.

Other flies like cluster flies, flesh flies, and fungus gnats may also occasionally fly out windows if there are indoor breeding sites. Larger horse flies or deer flies generally stay outdoors but could fly inside through an open door or window and then back out another one.

What happens right after a fly goes out a window?

Immediately after a fly is pushed out a window by a breeze, its instinct is to try to stabilize itself and start flying normally. A fly’s wings beat up to 200 times per second, allowing it to hover in place as well as fly in different directions.

If the window is only open a crack, the fly may frantically fly around near the window attempting to get back inside. Most houseflies and drain flies cannot survive outdoors for more than a few days. If the window is fully open, the displaced fly will either:

– Hover or land on the outside wall, window sill, or screen. From here, it may try to return inside through the open window or another nearby entry point.

– Get picked up by air currents and blow further away from the building.

– Lose control due to strong winds and drop straight down past the window.

A fly’s small body essentially turns it into a “falling leaf” when blown about by winds. It gets carried wherever the prevailing breeze takes it unless it can stabilize itself and start flying purposefully.

Factors determining a fly’s chance of survival

Several key factors affect whether a fly is able to survive after being displaced out a window:

Height of the window – Windows on higher floors mean longer falls for flies that cannot stabilize themselves quickly. Most houseflies cannot fly well above 6 feet high. The higher the window is off the ground, the less likely the fly will be able to take off and land safely.

Wind speed – Strong steady winds or sudden gusts reduce a fly’s control in the air. Sustained winds over 10 mph can fully lift and carry flies away.

Precipitation – Rain or snow will quickly weigh down a fly’s body and wings, causing it to drop. Mid-air moisture also impedes their ability to generate lift with their wings.

Temperature – Frigid or hot outdoor temperatures lead to lethargy and reduced flying ability in flies. They thrive in temperatures between 70-90°F.

Obstructions/surfaces – An open window over a hard surface (e.g. concrete) gives the fly little chance to stop itself from falling. Nearby structures, vegetation, or bodies of water improve its chances to land safely.

Age/health – Younger, healthier flies have better flying skills and control to prevent or recover from falls. Older or ill flies are weaker fliers.

What happens if the fly keeps falling?

After an initial period of struggling to reorient itself, if a fly is unable to stop its momentum and continues falling further from the window, it will likely suffer severe injury or die on impact with the ground.

Small flies like fruit flies and drain flies have very little mass. If they fall directly onto concrete or hard-packed soil, the force is usually enough to kill them instantly even from 1-2 stories up. Their lightweight exoskeleton splits apart from the sudden impact.

For larger houseflies, a long fall can lead to injuries like:

– Broken or deformed wings preventing flight.

– Ruptured exoskeleton and internal organ damage.

– Shattered leg joints.

– Concussion or paralysis from hitting the ground.

The higher the fall, the greater the speed they will build up during descent. Quickly decelerating from 30+ mph to zero when they hit the ground exerts tremendous pressure on their small bodies.

While the impact may not kill them instantly, severely injured flies are very vulnerable. Without the ability to fly and evade predators, immobilized flies quickly fall victim to other insects, spiders, birds, or lizards that eat flies.

What surfaces improve a fly’s odds of surviving a fall?

Falling onto certain soft or irregular surfaces gives flies a better chance of escaping a long fall out a window alive:

Bodies of water – Hitting deep/smooth water feet-first allows a gentle deceleration as the fly penetrates the water tension. However, they often drown if unable to reach the surface.

Mud/marshy areas – Wet muddy ground has more “give” to cushion the landing. The mud also helps trap them so they avoid getting swept away.

Foliage – Branches and dense vegetation help break long falls incrementally. Leaves distribute the impact instead of an abrupt stop.

Lawns/brush – Long grass, thick ground cover, and shrubs also provide a softer landing zone.

Sand/loose soil – Particulate matter shifts around during impact, absorbing some of the collision force.

Snowbanks – Fresh powdery snow acts like a thick cushion for lucky flies that hit it versus packed snow or ice.

Spiderwebs – Webs strung between vegetation can trap airborne flies and prevent them from falling all the way to the ground. The stickiness helps absorb their momentum.

Factoring in fly biology and behavior

Some aspects of a typical fly’s biology and instincts also give it a better chance at initially staying airborne or recovering after falling out a window:

Robust flyers – Stronger fliers like horse flies and deer flies are better able to counteract winds and avoid slamming into surfaces after getting displaced.

Spread wings – Flies extend their wings out sideways to create drag and slow a freefall. This increases their surface area to momentarily stay aloft.

Righting reflex – Specialized halteres organs behind their wings help flies sense body orientation and rotate themselves upright. This improves control as they are blown about chaotically.

Aerial recovery – Within their flight envelope, flies can perform rapid evasive maneuvers to avoid obstacles. At close range their reaction time is under 30 milliseconds.

Leg grasping – Built-in claws and sticky foot pads allow flies to firmly latch onto surfaces on contact to avoid bouncing off.

Exoskeleton flexibility – Their external skeleton bends and compresses on impact rather than shattering. This protects internal organs from rupturing.

Reduced injury susceptibility – Flies lack pain receptors and do not go into shock. Even after major injury they can still attempt to fly or walk if any limbs remain functional.

How far can flies fall and survive?

For a typical housefly, the chances of surviving a long fall diminish rapidly beyond these rough thresholds:

– 6-10 feet – 75% survival rate

– 10-20 feet – 40% survival

– 20-40 feet – 15% survival

– 40+ feet – Less than 5% survive

This can vary based on size, age, overall health, and outside conditions at the time. Larger horse flies or deer flies may tolerate slightly longer drops given their robust builds. Tiny fruit flies and gnats are proportionally more vulnerable to long falls and high winds.

The world record for a fly surviving the longest verified fall is 45 stories or approximately 623 feet! In a famous 1958 experiment, entomologists in Boston released houseflies out of tall buildings. One exceptionally lucky fly lived after falling from the roof of the Custom House Tower and landing on a concrete sidewalk below.

However, the vast majority of flies plunging from extreme heights do not survive. The normal statistical odds are strongly against them, even factoring in their aerial abilities.

Why can flies survive higher falls than humans?

There are several key reasons houseflies and other flying insects can withstand falling from heights over 600 times their body length while most humans suffer severe injuries falling only 2-3 times their height:

Lower terminal velocity – The max speed of a falling fly levels off around 30 mph versus 120 mph for humans. This results in less violent abrupt deceleration when they hit the ground.

Lower weight – Typical flies weigh less than 10-25 milligrams versus 110-200 pounds for humans. Their light mass means collisions have much less absolute force.

Exoskeleton – The external chitinous shell and flexible joints redirect impact energy rather than hard bones fracturing and transferring injury directly to organs.

No vital organs in “head” – A fly’s head capsule contains no vital systems, minimizing trauma from direct head-first collisions.

Decentralized anatomy – Flies have redundant sets of many organs (e.g. multiple hearts and stomachs). This increases the chances some remain functional after crash impacts.

Rapid recovery – Short lifespans and high metabolism allow flies to heal quickly from severe injuries that would permanently disable larger animals.

So while the height from which a fly can survive a fall seems disproportionately huge compared to humans, it makes sense given their vastly different anatomies and physiologies. Their small size and ability to temporarily arrest their descent mid-air with their wings gives them an advantage for survivinglong plunges.

Can a falling fly directed itself back inside through a window?

It is highly unlikely a fly would be able to deliberately direct its fall back through the original open window it was displaced from, or intentionally maneuver itself over and back inside from outside.

Flies essentially get blown wherever ambient winds and air currents take them once they lose control after falling out a window. They lack both the aerial speed and navigational ability to selectively return through a specific window opening high up on a building.

There are some scenarios where a fly might end up back inside shortly after falling out if:

– It lands on the outer wall/sill and immediately walks or flies back in through the open window.

– It gets blown near another open window or door and quickly flies inside before getting carried away.

– It falls onto a surface like a balcony or overhang that allows it to reorient itself and seek out the original open window.

However, purposely navigating back to the exact same window is unlikely given flies’ limited vision range and cognitive capacity. Once displaced outside, their priority is stabilizing themselves and finding the nearest shelter rather than locating a distant specific opening. Getting back inside usually depends on luck rather than intention.

Do flies ever intentionally fly out windows?

It is rare for a fly to deliberately and voluntarily fly out an open window. Some circumstances where this may occur include:

Pursuing food odors – Following attractive scents of nearby garbage cans, compost piles, or outdoor grills that waft in through windows.

Finding mates – Insects like cluster flies seek open windows and doors during spring mating swarms.

Foraging for supplies – Flies may purposefully venture out to locate suitable food and breeding sites then return.

Escaping indoor threats – Being startled by movements like swatting may spur them to rush towards windows and fly outside reactively.

Following other insects – If other flies or flying bugs zip out a window, they may instinctively follow without caution.

However, flies do not have strong enough vision and spatial awareness to purposely identify an open window from a distance and intentionally fly through it to “escape” outdoors. Their small size and rapid reflexes cause them to simply blunder out through any sudden openings that appear nearby. Once outside, finding their way back in is difficult. So the risks usually outweigh any potential benefits for flies to voluntarily fly out windows.


A fly’s fate after getting blown out a window depends heavily on factors like fall height, weather, and luck in terms of landing surface. The most likely outcomes range from stunned to severe injury to instant death upon impact with the ground or other obstacles. However, flies’ lightweight bodies and ability to temporarily glide or brake descent improves their odds of surviving longer falls compared to many animals. While disorienting and dangerous, getting blown out a window does not inevitably doom a fly thanks to its unique flying capabilities and resilience. With some fortune, it may be able to regain control, land safely, and resume its normal activities after such an ordeal.