#974 Can insects fly in the rain?

Can insects fly in the rain? They pretty much all can, but many of them choose not to. Some do fly during the rain. It depends on their size, the temperature, and their ability to resist water. Interestingly, larger insects have more need to hide than smaller insects do.

When the day is warm, insects fly around freely. However, as soon as it starts to rain, they have pretty much all vanished. What happens? Firstly, let’s look at why the insects disappear. Raindrops don’t do any damage to us, but if the raindrops were larger than we are, we would need more than an umbrella to venture outside. This is the case for most insects. The average raindrop weighs 0.034 g, which doesn’t sound like a lot, but the average butterfly weighs 0.3 g. If a butterfly gets hit by a raindrop, they are being hit by one tenth of their weight in water. If we were trying to walk down the street and we got hit by a tenth of our weight in water every few seconds, we would have trouble walking in a straight line. Most insects have the same problem. If they flew during the rain, every raindrop, or even the wind of the raindrop passing them, would knock them down or off course and they would have to spend too much energy trying to fly. It is easier for them to just hide under a leaf until the rain has passed.

Butterflies and most insects could fly during the rain if they had to. Butterflies and many other insects have evolved a series of microscopic bumps all over their wings. These break up the impact of a raindrop, reducing the force and knocking it off much more quickly than if their wings were smooth. The bumps also help to strengthen the wings in case of impact. Still, it is easier not to fly. If there is a rainstorm, you can often find a lot of insects if you look under leaves.

The temperature is also a reason why insects don’t fly in the rain. Not always, but rainfall is usually accompanied by a drop in temperature. Insects are cold blooded and if it is too cold, they literally cannot fly. We can make heat by moving our muscles but insects need heat before they can move their muscles and fly. Also, if they were hit by a raindrop, the water would pull even more heat out of their bodies, possibly proving fatal.

Insects know when it is going to rain because they can predict the weather. They do this in three ways. Firstly, the sense the drop in temperature that comes before rain. Secondly, light is scattered more by rainclouds than by other clouds and insects can see this scattering. And, lastly, they are able to sense atmospheric pressure. Pressure always drops before a rainstorm and when the pressure drops, the insects go and hide.

Interestingly, mosquitos have absolutely no trouble flying in the rain and rain can actually bring out even more mosquitos. There are several reasons for this. The first is that mosquitos are tiny. Raindrops don’t seem to be that far apart, but if you are the size of a mosquito, there is a lot of space between the raindrops, The chance of them actually getting hit by a raindrop is slim. Secondly, as raindrops move through the sky, they push the air in front of them, making a wake similar to the wake of a boat travelling through water. We wouldn’t be able to feel this wake, but it is enough of a force to push a mosquito sideways, out of the way of a raindrop. Thirdly, mosquitos tend to live in very warm places and rainfall in those places doesn’t necessarily lower the air temperature very much. They are usually very humid places and it is often warm rain. This doesn’t cool the mosquitos down. And, lastly, if a mosquito is hit by a raindrop, it doesn’t kill them. When a mosquito is hit by a raindrop, it is enveloped by the water and forced down to the ground. They are not killed by the water, though, because they have water repelling hairs that allow them to escape from it. They pause for a bit, and then head back up into the air. And this is what I learned today.

Photo by Pixabay: https://www.pexels.com/photo/rain-drops-459451/

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