Students are crossing the bridge over the campus pond, unaware of the minuscule egg being laid below their feet, in the underwater forest. The egg gently sinks to the bottom. After while, a nymph appears. It lives under water for no less than a year, until it emerges as a full-grown common blue damselfly and takes to the air in spring.
Dozens of bright blue black-striped toothpicks that seem to give off light in the sun can be seen whizzing around just above the surface of the water. They like ‘clean’ water, says ecologist Garry Bakker of Bureau Stadsnatuur, and that’s exactly what they find in this ‘basin of bare concrete’. The pond was built just over a decade ago, so it hasn’t had much time yet to gather a lot of organic material.
The damsels are quite busy near the pond. True hunters, they shoot past in all directions, looking for prey. And there is plenty of that in this ‘underwater tropical rainforest’, says Bakker. The largely submerged water plants are a habitat for all kinds of tasty morsels, such as bugs and mosquitoes. And occasionally the damselflies whiz past the enormous eyes of an emperor dragonfly which, with its back curved, is busy laying its eggs into the water plants.
The sight reminds our damselfly of what may well be his most important mission: to find a mate, as soon as possible. From the moment he emerges from the water, he has a few months at most to live and pass on his genes to the next generation. But these are not damsels in distress. If you look carefully, you’ll see pairs of them flying around all over the place – with their bodies attached to one another, sometimes in the shape of a heart.
With the female, which often has a different colour, the male flies off to a nice spot where she can deposit her eggs under water. The eggs gently spiral down to the bottom – and you know how it goes on.