How Do We Know Insects Can’t See Red Light?!

Ever wondered if insects can see red light? Or how on earth we figured out the answer?! Me too.

This article will lay out exactly why insects as a group tend not to be able to perceive red light waves. Not only that, it’ll also explain the experiments scientist used to determine what wave lenghts of light insects are sensitive too.

Scientist use a combination of observational experiments and also technical experiments to determine if insects can see and perceive red light. Through these experiments they have conclusively agreed that the vast majority of insects can not see red light.

So let’s get into it…

What experiments reveal that insects can’t see red light?

Technical experiments to detect red light sensitivity

There are a couple of ways to go about finding an answer to this question. The first would be a technical approach involving monitoring the biology of a variety of insects while exposing them to a variety of light ways (including red light) and determining if there was a difference.

For instance if there were electrical impulses fired in the nerves of the insect (a fly for instance) when exposing it to blue light but not descernable messurment could be found when showing red.

This would be an indicator that the fly is not detecting the red light whilst also confirming that the fly is sensitive to blue light.

What about observational experiments?

The other approach, which is also just as valid and probably worth running in tandem to back up the technical tests would be observation of behaviours.

What I mean by this is that it would be feasible to set up an experiment where you trained a group of insects (lets stick with flies for our example) and trained them to associate a color with a reward, sugar water for instance.

Then if you used in our case a block of red color and the flies behaviour didn’t change. It would be a strong indicator that the flies could not perceive the color and as such no association with the sugar water reward.

Not all insects see in the same way

Some colors will appear more pronounced for say a honey bee than they would a fly. This is likely due to the fact that they have evolved over time to associate certain colors with nectar which is important for bees.

Where as it is less important for flies and as such they don’t potentially percieve certain colors as vividly.

Going into detail about the way in which each group of species of insects interprets color is a pretty huge topic. But one thing they all share in common is a lessened sensitivity to red light.

Why Red Light

Would it surprise you to know that insects aren’t the only group of animals that aren’t sensibite to red light?

Many of the deep ocean going species don’t perceive red light either. I suspect this is due to the fact that red light waves are shorter than say ultraviolet.

As a result they don’t penetrate the ocean depths far enough. So the nature of the animals that reside in the depths didn’t find the need to interpret red wavelengths of light.

Cool right!

Red light in insects

Ok that’s all good and well for creatures of the deep ocean. But that doesn’t explain why insects can’t see it. I mean there’s lots of red light sources on land. Just think of all the red roses!

The answer is quite interesting. You see insects in general can perceive light from a area of the spectrum that moves more towards the ultra violet end.

Humans can’t perceive ultraviolet light, its just beyhond the blue ‘end’ of the spectrum. I put end in quotes because it’s only the end relative to what humans perceive. And is not infact the actual end of the light spectrum.

This means that nature through evolution has determined that it is more useful in general for insects to perceive ultraviolet light rather than red light.

The reasons for that I’m not entirely sure, if you are interesting in an answer let me know and I’ll write and research an article answering that very question.

Does that mean I can plant a bunch of red flowers in my garden and insects won’t touch them?

Ha smart idea! Unfortunetly insects don’t rely on just their vision to detect potential food sources. And just because they can’t see red, that doesn’t mean that your ‘red’ flower isn’t emitting ultra voilet colors that are imperceivable to humans.

They can also rely and scents and smells emitted from the flowers themselves. After all the plants themselves benefit from pollinators so in some circumstances it’s of mutual benefit to the flower and the insect to attract one another.

Are there any insects that can see Red light at all?!

There’s always an exception to the rule and there is some evidence to suggest that certain butterfly species can perceive red light. This might again be due to a new to find new food sources.

But in all honestly there juries out on this one and as a general rule insects will not be about to see red light sources.

That being said, in 10 years time with more research carried out by scientists this answer may change!

Red light doesn’t affect your night vision!

Slightly off topic, but this came up during my research on bugs and red light. You’ll often see that head torches sometimes have a red light mode. Or are exclusively red light only.

This is because when you use red light at night and it’s pitch black, it tends not to affect your night vision.

Using a regular torch to illuminate the surrounds is all well and good. But the minute you turn it off or look another way, you’r eyes have to readjust to the night. So keeping your torch set on red light mode is a cool tip!

Can we use this fact to our advantage?

That’s an interesting question and the answer is yes we can! For instance have you ever noticed moths hovering around an outdoor light source?

It’s irresistible for them. However what if you replaced that white light with a red light. You might find that you don’t attract as many insects around your camp site or porch!

The other use-case I can think of is for observing these creatures undisturbed. They would happily continue on without noticing the new red light source.

Summary

So there you have it. Now you know how we discovered that insects can percieve red light. Not only that, red light isn’t interpreted by a bunch of different categories of animals.

To further this point, we used the example of deep sea fish. But squids and spiders are also obvlious to red.

Using simple experiments scientists can determine insects can decern red, blue, yellow, green from one another will a excellent level of accuracy and confidence.

That being said, we might be having a different conversation in the future when new discoveries are made about these amazing and vitally important creatures.

If you want to learn more about various insects, then checkout our site categories, we have a bunch of articles there that are totally worth reading:

P.S.

That’s it for this article. I hope you enjoyed reading it and if you think it might be useful for someone else then please share it on social media, email or your own website! It really encourages us to write more content and grow the site!

All the best

Steve