Why don’t insects die when they fall – The Curious Answer

If you have ever tossed an insect out of the window or watched as one tumbles off a shelf or the ceiling, you might be wondering why many insects don’t die when they fall, and whether all insects are protected from the damage caused by dropping from a height.

Most insects don’t die when they fall because they have a far higher ratio of air resistance relative to their body weight than most other creatures, which means they pick up speed much more slowly when they fall.

This also means that they have a much lower terminal velocity than that of, for example, a human being or a cow, and therefore, many can survive falling from any height.

In this article, we are going to look at:

• How does the size of an insect affect the damage it will sustain when it falls?
• What helps an insect survive a fall
• How far can different insects fall before it hurts them?
• Is any height too big for an insect to safely fall from?
• Are some insects better at surviving long falls than others?

Do Large Insects Suffer From Greater Fall Damage?

You might be wondering if a larger insect, which is likely to be heavier than small insects, is more likely to suffer from damage when it drops from a height due to its weight.

If you toss a big woodlouse out of a window, will it hurt itself after a fall that a small woodlouse would be unscathed by?

You may be surprised to learn that, despite the fact that a larger insect is likely to be more resilient, the answer is typically yes, large insects are somewhat more likely to suffer from fall damage.

A large insect may have a slightly greater surface area, which will increase the air resistance slowing it down, but it will also have a much greater mass.

This allows it to push past the air resistance much more effectively, and it will take far more air resistance to slow it down – meaning it falls faster.

All other things being approximately equal, doubling the size of an insect will increase its surface area by roughly a factor of four, but will increase its mass by closer to a factor of eight, resulting in its ratio of mass to surface area now being twice as big as it would be for a smaller version of the same creature.

Does this mean that an insect will accelerate towards the ground twice as fast as an insect of half its size?

No, it doesn’t. It merely means that the effect of air resistance on it will be half that of the smaller ones. However, even if there is no air resistance at all, objects near the surface of the Earth can only gain approximately ten meters per second of speed every second.

This means that no matter how heavy an object is, or how small its surface area is, gravity cannot make it move faster than thirty meters per second after it has been falling for three seconds.

Even so, thirty meters per second is very fast and far more than most creatures could survive when hitting the ground.

Fortunately for the insects, air resistance not only decreases how quickly they accelerate but also gives objects a maximum velocity that they will not exceed while falling.

For humans, this terminal velocity is somewhere around a terrifying 56 meters per second, but for insects this is vastly lower, allowing many of them to survive falls from any height.

Of course, working out what height an insect can safely fall from is not an easy problem. The density of an insect probably doesn’t vary too much, meaning that in theory, there should be a fairly direct relationship between the size of an insect and its ratio of mass to surface area.

However, the surface area is not necessarily a simple value that can be considered on its own.

Many spiders (technically not insects but not a bad model for some), especially the larger species, will fan out their legs while falling, greatly increasing the surface area that the air resistance has to act on and decreasing both the rate they accelerate at and the maximum velocity they can reach.

This defensive strategy allows them to survive higher falls than they otherwise would be able to.

How Far Can Insects Fall Before It Hurts Them?

This is again a tricky question in some ways, but essentially, if the insect has reached its terminal velocity within, for example, ten feet, anything greater than ten feet will make no difference.

As long as the terminal velocity is such that the insect will not be killed when it hits the ground, it makes no difference how far the insect falls.

This is because no more acceleration is gained by falling further, and it is the acceleration that is dangerous. If a human jumps off a step that is thirty centimeters tall, the human suffers no damage because they hit the ground at low speed.

If a human jumps off a step that is thirty meters tall, they will accelerate at an increasing rate until they reach their terminal velocity – but this is at such a great speed (due to the increased weight of the human) that it will kill them when they hit the ground.

However, we all know that if you add to the air resistance of a human, using a parachute, for example, the human will survive the fall, because their terminal velocity has been changed and they will fall far more slowly.

This reduces the impact, which makes the fall much safer.

As long as the air resistance equalizes with the weight of the falling insect before it has reached a falling speed that would kill it, the height it falls from should make no difference.

Are Some Insects Better At Surviving Falls Than Others?

Some insects might be better at surviving falls than others because they may have a greater surface area to weight ratio.

The amount of air resistance that is experienced by an object (or insect) is affected by its shape, its speed, its cross-sectional area, and air density in that area (which depends on factors such as temperature and altitude).

An insect that is broad and wide but very light, such as a flying insect, will survive a fall much better than a narrow, heavy insect such as an ant.

The air resistance created by its wings, coupled with its lighter weight, will ensure that it reaches its terminal velocity more quickly and therefore does not hit the ground with as much force.

In general, however, this is about the theory rather than the practical. Most animals that are the size of a mouse or smaller do not need to be concerned about falling unless they are particularly squishy (spiders may have issues) because they will reach their terminal velocity before they accelerate to dangerous speeds.

That means that very few insects, except perhaps some giant ones like the giant centipede, are really at risk of being damaged by falling. They can drop from great heights without sustaining any damage; they aren’t falling fast enough to be harmed.

What Else Needs To Be Considered?

You might be wondering what else comes into play when an insect falls, or whether these are the only aspects that need to be considered. It probably won’t surprise you to learn that they aren’t.

One of the key factors that are changing the amount of damage a fall inflicts is what kind of surface stops the fall. An insect that lands on a concrete surface are far more likely to be damaged than an insect that lands on soil or grass.

This is because the concrete has no give in it, and therefore cannot absorb any of the impact, so all of this force is transferred to the insect’s body, and if there is enough force, this will destroy its body.

Soil, however, has some give and will absorb some of the impact, lessening the force (and therefore the damage) that the insect is subjected to when it hits.

Surfaces with even more give, such as water, would do even less damage – which is why a human might survive a great drop if they landed in water.

Similarly, you need to think about the insect’s fragility, and this plays into its ability to survive a fall.

A very delicate insect, such as a crane fly, might be damaged by a fall that a woodlouse would survive.

Beetles are more likely to live through hitting the ground than caterpillars, because beetles have a hard shell to protect them, and are generally more robust.

Bottom line

Most insects don’t die when they fall – even from great heights – because they reach their terminal velocity quickly and are not falling very fast when they hit the ground.

Even if an insect is large and heavy, its terminal velocity is likely to be such that it will not be harmed by a fall, and few insects need to worry at all about falling.

Alright, that’s it for this article, here are a few hand-selected articles that you might also find interesting reads:

The Unlucky 13: Insects with the Shortest Life Spans

How Do Bugs Walk On Walls?! The Curious Answer

Top 10 fastest flying insects in the world