As a class of invertebrates, insects have survived, evolved and have been around longer than we have. We already owe many inventions, discoveries and lessons in nature to insects, so the next time you want to swat a fly, give a thought to the damage you are doing
As I saw a tiny fruit fly encircling a bunch of bananas, I thought to myself: How large and endless the world must seem to this insect with its tiny wings and bodyIJ Till about 100 years ago it was believed that fruit flies magically appeared from within rotting fruit. We do know now that it is not magic but an acute sense of smell. A fruit fly can smell a rotting piece of fruit from miles away. It might take a while to get to it, but get to it, it shall. like a lot of other insects, fruit flies have compound eyes. like we all studied in school, we know that compound eyes in contrast with our own eyes are immovable, unable to focus and are made up of thousands of individual photoreceptors.
The compound eye, in fact, evolved from a group of eyespots on a swelling on the surface of the head. Each eyespot evolved into a single photoreceptor called ommatidium, or simply put into a single eye with light-sensitive cells and a clear curved coating that acts as a lens. Each of these ‘single’ eyes which can number in thousands captures only a tiny part of the final image the insect sees. This is contrary to what we’ve seen in commercial science-fiction films where insects see multiple images like a kaleidoscope. like us, insects see only one image but do not have the same colour vision as us, lack clarity and detail and are short-sighted. In fact, butterflies which are one of most farsighted of all insects would be legally blind in human terms. The bumblebee can see only up to a range of half a metre.
The image an insect sees can be compared to a very low resolution pixilated image that has been scaled up on our computer screen. For better vision some insects increased their ‘resolution’ by having more and smaller ommatidia. Dragon flies have around 28,000 ommatidia in each eyes. In the insect world this would be like upgrading to a 10,000 mega pixel camera from a webcam! But even with so many photoreceptors the final image the dragonfly sees is nowhere near what the human eye sees, because the distance between the lens and the photoreceptor is only microns apart. Insects like the honeybee and dragonfly have through evolution increased the distance between lens and receptor resulting in enormous bulging eyes and better vision.
Many species of insects see a much broader spectrum of light than we can with the exception of the red spectrum. like a lot of other insects, bees can see in the ultraviolet spectrum and as nature designed it, flowers reflect ultraviolet light. In the 50s researchers at the Imperial College london developed the Floral Reflectance Database which enabled them to see for the first time what the world looks like through the eyes of a bee.
What was revealed was amazing. They found that many flowers actually had ultraviolet patterns on their petals and were presumably acting like landing strips or beacons for bees looking for nectar. What would appear to be a yellow flower to us would look very different to a bee which can see patterns and colours completely invisible to us. They also found that bees see the world almost five times faster than we do. No surprise when you consider that fast flying insects would need high speed vision to escape predators, hunt and like some insects, to catch their mates in mid air. That’s why swatting a fly is so hard, besides a large field of view, a fly’s eyes is processing images so fast that you could say it almost sees thing in slow motion.
Another amazing finding by a study led by Daniel Robert has shown that bees can sense and distinguish between the electrical fields of flowers. Bees were using the electrical field as a guide to which flower to visit and were also able to work out which flowers had already been visited by other bee.
Just because insects see in a much lower resolution and are short-sighted doesn’t mean they can’t see what we can see as well. An ant can also see the sun, just like we can. The sun is 93 million miles away so how can an ant who’s head is barely a millimetre away from the ground even be aware of the existence of the sunIJ Amazingly, the fact of the matter is that many insects navigate using the sun, moon and even the stars.
This could explain why moths fly around light. As the case is quite often there is no definitive explanation for this phenomenon, but there are some plausible theories.
Some moths are known to migrate and some scientists have suggested that moths may be using the moon as a reference point and have the ability to chart their flight paths to the moon. Moths may actually be getting confused and disoriented with bright sources of artificial light all around that, unlike the moon, don’t move across the sky. Since a moth’s light intensity adapting mechanism responds much more slowly to darkness than to light, once the moth comes close to a bright light, it might have not leave because it would be literally blinded by the darkness.
A recent study from researchers in Sweden and South Africa found that on moonless nights, dung beetles were actually using the stars to orient themselves. Dung beetles like their name suggests feed on animal dung and seek out steaming piles of it. Once they locate a pile they form it into little balls and then roll them away. The beetle must find the fastest and shortest route away from the pile to avoid any thieves and competitors. Researchers discovered that on moonless nights, dung beetles were using the milky way to navigate. In the experiment the researchers put the beetles under controlled conditions in a planetarium and found that when they projected a dark starless sky the beetles were disoriented and appeared lost, but when they projected the milky way all the beetles followed a particular path.
As a class of invertebrates, insects are very successful and have survived, evolved and have been around longer than we have and we are only beginning to understand how they perceive, navigate and continue to populate their world. We already owe many inventions, discoveries and lessons in nature to insects, so next time you want to swat a fly give a thought to who the more evolved being is.
(The writer is a wildlife film-maker)