Science Illustrated



Dragonflie­s change colour in the name of love.

This mature male dragonfly pauses in his endless quest for either mate or prey, to rest for a moment on the dried husk of a seasonal flower. Not so long ago he lived at the bottom of a nearby swamp, the terror of smaller insects and even tadpoles. Now, he’s master of the sky within his tightly held territory. His wraparound eyes give him constant surveillan­ce, and he’s always ready to seize prey, chase off a challenger or dance for a prospectiv­e mate.

Dragonflie­s are incredible predators, and catch over 95% percent of the insects they target - that’s a much better kill rate than the leopard (38%) or even a great white shark (around 55%). If you are a bug, and a dragonfly wants to eat you, you might as well just let it happen...

This dragonfly’s incredible colouring signifies he is sexually mature. Dragonfly nymphs are mostly a sort of drab brown, and newly hatched adults can be yellow or black-and-orange. As the dragonfly grows, a chemical reaction takes place within the pigments in its exoskeleto­n, slowly turning the insect bright red.

Scientists don’t yet understand the precise mechanism that causes the change, but they’ve been able to replicate it using vitamin C. It’s possible the change occurs as the dragonfly is exposed to sunlight, since these insects rely on vision to identify each other - mates and rivals alike.

Dragonflie­s are one of evolution’s greatest success stories. An ideallyada­pted predator that rarely misses a meal and dominates its environmen­t both as an adult and as a nymph. In previous geological eras, when the oxygen levels in the atmosphere were much higher, some dragonfly species grew to have metrewide wingspans. Imagine having to clean one of those out of the car’s radiator...

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