Extraordinary Insects. Anne Sverdrup-Thygeson

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.

       Go to the Ant and Be Wise

      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 insects are the ones who look for food in lots of different places and also form close bonds with one another; in other words, the ones that live alongside many others in a community. These critters must constantly be making judgements: is that yellow thing over there a flower with sweet nectar or is it a peckish crab spider? Will I be able to carry that conifer needle alone or will it take several of us? Do I need to take a sip of this nectar to keep myself going, or should I take it home to Mum?

      The social insects divide up jobs, share experiences and ‘talk to each other’ in an advanced way. This requires capacity for thought. To cite Charles Darwin in The Descent of Man: ‘The brain of an ant is one of the most marvellous atoms of matter in the world, perhaps more so than the brain of a man.’ And that was without knowing what we now know: that ants are capable of teaching skills to other ants.

      The ability to teach has long been seen as exclusive to us humans, almost a proof of an advanced society. Three quite specific criteria distinguish teaching from other communications: it must be an activity that only happens when a teacher meets an ‘ignorant’ pupil; it must involve a cost for the teacher; and it must make the pupil learn more rapidly than he/she otherwise would have. The term is used for communication about concepts and strategies, so the honeybees’ dance (see here), which is more about process, is generally not viewed as teaching. However, it turns out that ants are capable of teaching things to other ants, through a process known as ‘tandem running’, in which an experienced ant shows the way to food. This occurs in a European species, Temnothorax albipennis, which relies on landmarks such as trees, stones and others, as well as scent trails, to remember the way from the anthill to a new source of food. In order for several ants to be able to find the food, a she-ant (all worker ants are female, see here) who knows the way must teach it to the others. The teacher runs on ahead to show the way, but constantly stops to wait for her pupil, who runs more slowly, apparently because she needs time to take note of the landmarks they are passing. When the pupil is ready again, she touches the teacher with her antennae and they continue on their journey. The behaviour therefore satisfies the three criteria of ‘genuine teaching’: the activity happens only when a teacher meets an ‘ignorant’ pupil, it involves a cost for the teacher (she must stop and wait) and it makes the pupil learn more quickly than she would have on her own.

      Bumblebees have also recently been inducted into the exclusive little group of creatures who can teach tricks to their peers. Swedish and Australian scientists successfully trained bumblebees to pull on a string to gain access to nectar. They made artificial blue flowers in the form of plastic discs, which they filled with sugar water. When these were covered with a transparent plate of plexiglass, the only way of gaining access to the sugar water was to pull on a string attached to the fake flower. If the scientists only let untrained bumblebees loose on the covered flowers, they didn’t understand a thing: none of them pulled on the string. A great starting point. Then the bumblebees were given a chance to get acquainted with the ‘flowers’, learning about the reward they offered. Gradually, the fake flowers were pushed further and further beneath the transparent plexiglass plate. This time, when the fake flowers were finally pushed fully beneath the plate, 23