shaft. The whole thing is attached to a kind of pump in the head, which creates suction, allowing the fly to hoover up the yummy nutritious soup.
Houseflies’ poor table manners and somewhat varied diet, which includes items such as animal dung, are the reasons why they spread infection. The flies aren’t dangerous in themselves, but like used syringes, they can carry infections and pass them on to us.
And now I think about it, maybe it’s just as well we humans taste with our tongue and not our feet. Blueberry shrubs are one thing, but the thought of going around tasting the insides of your shoes all winter long is hardly appealing.
Insects’ senses are adapted to their environment and needs. Whereas dragonflies and flies need good vision, cave-dwelling insects may be totally blind. Insects that come into close contact with flowers, like honeybees, can also see colours, but their colour spectrum is shifted upwards so that they don’t see red light. On the other hand, they can see ultraviolet light, unlike us humans. This means that many flowers we see as monotone, such as sunflowers, have distinctive patterns for a bee, often in the form of ‘landing strips’ that direct them towards the source of nectar in the flower.
Insects’ compound eyes consist of many individual eyes. The brain merges all the tiny pictures together into a single large image, although it is coarser and fuzzier than the way we humans see the world (it looks a bit like a low-res photograph on your PC screen when you’ve zoomed in too close). There are plenty of reasons why insects don’t have driving licences, of course, but sight is a big one: they would never be able to read a road sign at 20 metres as the image would be too blurry. That said, their vision is supremely adapted to the tasks that will fill their days. Take whirligig beetles, for example: shiny black pearls of beetles that dash around on the surface of the waters of our lakes. They have two pairs of eyes, with different refraction: one pair for seeing clearly underwater so that they can watch out for hungry perch, and another for seeing clearly above the water so that they can find food on the surface.
Insects can also see a property to which we humans are blind: polarised light. This has to do with which plane the light is oscillating in, and it alters when sunlight is reflected – in the atmosphere or on a shining surface like water. But let’s go easy on the physics and restrict ourselves to saying that insects use polarised light as a compass that enables them to orientate themselves. We humans only relate to polarised light when we put on a pair of Polaroid sunglasses to reduce the glare of reflected light.
In addition to having compound eyes, insects may also have separate simple eyes, whose main function is to distinguish between light and dark. Next time you encounter a stinging wasp, look deep into its eyes and note how, in addition to the compound eyes on either side of its head, it has three simple eyes in a neat triangle on its forehead.
The World’s Most Skilful Hunter Sees You and You and You . . .
When it comes to having eyesight adapted to their daily business, dragonflies are in a class of their own: their vision is a major reason why these insects are deemed to be among the world’s most efficient predators.
Lions may put on an impressive display when hunting in a pride, but the fact is that they only manage to chase down their prey one in every four times. Even the great white shark, with its terrifying 300-toothed grin, fails in half of all its attempted attacks. The dragonfly, however, excels as a lethal hunter, succeeding in more than 95 per cent of its attempts.
Part of the reason why dragonflies are such skilled hunters is their extraordinary command of the skies. Their four wings can move independently of one another, which is unusual in the insect world. Each wing is powered by several sets of muscles, which adjust frequency and direction. This enables a dragonfly to fly both backwards and upside down, and to switch from hovering motionless in the air to speeding off at a maximum speed of close to 50 kilometres an hour. No wonder the US Army uses them as models when designing new drones. But their vision also makes a significant contribution to their success. And it is perhaps hardly surprising that they have good eyesight when almost their entire head consists of eyes. In reality, each eye is made up of 30,000 small eyes, which can see both ultraviolet and polarised light as well as colours. And since the eyes are like balls, the dragonfly can see most of what is happening on all sides of its body.
Its brain is also prepped for super-sight. When we humans see a rapid sequence of images, we see them in a flowing movement, a film, if there are more than around 20 images per second. However, a dragonfly can see up to 300 separate images per second and interpret every single one of them. In other words, a cinema ticket would be quite wasted on a dragonfly. Where you and I see a moving film, it would simply see a very rapid slide show – one long stream of separate snapshots or frames.
© Carim Nahaboo 2019
The dragonfly brain is also capable of focusing over time on one specific section of the enormous quantity of visual impressions being received. They have a kind of selective attention that is unknown among other insects. Imagine you’re travelling across the sea in a boat and see another boat ahead of you, at a given angle to you. If you ensure that you always have the boat at exactly the same angle in your field of vision, you will end up meeting. In a somewhat similar way, the dragonfly brain can lock its attention on approaching prey, coordinating its speed and direction to ensure a strike – and yet another successful hunt. Intricate, well-designed sensory organs alone are not enough: you also need a brain that can process all the information as it streams in, seeking out relevant patterns and connections, and sending the correct messages out again to different parts of the body. And even though insects have tiny little brains, we will see that they are a lot smarter than we might assume.
Carl Linnaeus, the great Swedish biologist who classified our species, placed insects in a separate group, in part because he believed they didn’t have brains at all. Maybe that’s not such a surprise, because if you behead a fruit fly, it can live pretty much as normal for several days, flying, walking and mating. Eventually, of course, it will starve to death, because no mouth means no food. The reason why insects can survive in a headless state is that they don’t just have a main brain in their heads but also a nerve cord running through their entire body, with ‘mini brains’ in each joint. Consequently, many functions can be performed regardless of whether or not the head is in place.
Are insects intelligent? Well, that depends on what you mean by intelligence. According to Mensa, intelligence is the ‘ability to acquire and analyse information’. Now, it’s unlikely that anybody’s going to argue that insects deserve to be members of Mensa, but the fact is that they never cease to surprise us with their ability to learn and make judgements. Some things we believed to be the sole preserve of large vertebrates with proper brains also turn out to be within the capabilities of our tiny friends.
But not all insects are created equal, and there are great differences between them. Those with dull lives and simple habits are the least bright. You don’t need the wisdom of Solomon if you’re going to spend most of your life snugly tucked up in an animal hide with your sucking snout stuck in a vein. However, if you’re a honeybee, a wasp or an ant, you’re more in need of intelligence. The cleverest
