The Perfect Killer

mainLions and white sharks are top-level predators, but compared to the superior hunter of the world of insects, they’re rank amateurs. Nature has made the dragonfly an efficient killing machine, whose sophisticated vision, unrivalled flying technique, and jagged jaws make it almost impossible for prey to escape.

The dragonfly predicts the future position of the prey.
When humans play ball, we calculate the path of the ball, so we can catch it at the perfect time. For a long time, scientists believed that the ability to calculate a ball’s or prey’s distance, direction, and speed in a matter of a few milliseconds required a highly complex brain. Even sophisticated predators such as lions place themselves in the path of the prey when they follow it, instead of crossing the path of the prey. When a team of scientists monitored dragonflies with a camera, it turned out
that the insects cross the path of their prey at just the right time instead of tailing it.

Target: Locked On
Even when the dragonfly faces a swarm of insects, it is able to focus 100 % on one single victim without being distracted by other objects. Until recently, scientists believed that only humans and monkeys were able to focus on one thing at a time and exclude everything else. The discovery that dragonflies also have this useful ability was made by scientists from the University of Adelaide in 2012.

By means of a tiny glass probe with a 60 nanometer point – 1,500 times thinner than a human hair – the scientists mea-sured nerve activity in the dragonfly brain, indicating that it had the capacity for selective attention. At the same time, they discovered that dragonflies, which are introduced to two possible victims
at the same time, are able to lock on to one and ignore the other. As dragonfly prey often flies in swarms, this capacity is a great advantage. As soon as the dragonfly has selected its prey, the brain filters out all other targets and only focuses on the selected meal. Scientists hope that the discovery  will inspire engineers to develop an intelligent robot based on the dragon-fly’s simple, but highly efficient nervous system.

eyes

Eyes provide panoramic vision
The dragonfly’s sophisticated eyes give it outstanding vision and a massive advantage over its prey.

Like in other insects, the dragonfly’s eyes are made up by many individual eyes, or ommatidia, with one sensory cell each. A fly eye only has 6,000 ommatidia, whereas a dragonfly’s vision is made up of 30,000. This enables it to both take in its surroundings in one look and focus sharply on one single victim. Moreover, the dragonfly’s eyes features 4-5 so-called opsins – light-sensitive proteins – whereas humans only have three. Apart from ordinary colours, dragonflies can also detect UV light, which is invisible to humans. In the upper part of the eye, you find the opsins, which detect blue and UV light, and in the lower part, you find the ones that detect green and orange. The dragonfly thus sees the sky as white, making a dark, flying victim stand out clearly.

No blind spots
The big eyes wrap the dragonfly’s head like two hemispheres, resulting in a 360 degree view.

Unlike most other insects, which cannot see what happens behind or underneath them, the dragonfly can see and escape its enemies no matter the angle of attack. At the same time, it utilises the other insects’ weakness, often attacking them from their blind spots. The dragonfly’s complex eyes also allow it to divide its vision into sectors, or a type of coordinate system. By “locking” a moving victim into a certain position in the coordinate system, the dragonfly can focus very accurately on it and follow it with its eyes.

wings

The Ultimate Biological Helicopter
The four wings provide dragonflies with a manoeuvrability, that aircraft engineers dream of.

The dragonfly’s wings are so exceptional that the US military and NASA are working on drones using flight controls inspired by this mere insect. The wings are light, stiff, yet flexible at the same time. Moreover, a dragonfly can move its four wings independently of each other, enabling it to reverse direction very fast. In the case of ordinary flight, the wings beat slightly out of stroke, so the forewings produce a vortex, which the hind wings use to generate more lift. In order to make a sharp turn, the wings of one side beat forwards, while those of the other side beat backwards. The dragonfly can also hover in the air like a helicopter by moving the forewings downwards, while the hind wings beat upwards, and vice versa. The dragonfly can even fly upside down, if necessary. Only one other insect matches the flying qualities of the dragonfly: the damselfly, which is a close relative.

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Jaws pulverise the prey
Dragonflies belong to the scientific order of Odonata. The Greek word means something like “toothed” – a suitable name for the dragonfly, which pulverizes the prey into a mash with its saw-toothed jaws.

Even to another, smaller dragonfly, a close encounter with this predator means death. The dragonfly works systematically to make its prey defenceless. First, it holds on to the prey with its forelegs. Subsequently, it cuts the wings off the prey, so it cannot escape, and if the prey still fights back, it is bitten in the head. Finally, the dragonfly can have its meal in peace, starting with the head. The dragonfly’s jaws can be opened wide, allowing it to chew even large insects. And it does not even need to land to eat. The prey is often crushed in the air – a clear advantage, when the dragonfly’s insatiable appetite is to be satisfied. The glutton hunts flies and mosquitoes almost around the clock, and it is not above consuming its own peers. Scientists estimate that a dragonfly consumes 10-15 % of its own body weight every day. Even when a dragonfly faces death, it does not stop eating. Scientists know examples of dragonflies captured
in a spider web, which ate the spider.

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