Every possible surface of the pond is dotted with snails. I do mean every surface: at first I thought there had been a massive die-off because I saw so many floating. But a closer look revealed that these snails weren’t dead; they were actually gliding along the pond’s surface from beneath it, so that their slimy bellies faced upwards. It’s hard to tell if they’re buoyant or relying on surface tension.
The pond’s surface is also strewn with seeds. They look like tiny maple keys – about half the width of my thumb – and I have no idea what they are. (Homework!)
The other common invertebrate could not be more different from the ever-patient snails, though it also shares a propensity for inversion. Backswimmers* (known as notonectids to their friends, of which there aren’t many) are hemipterans who use their paddle-shaped back legs to propel themselves upside-down underwater. They’re tiny predators that seem beautifully aquatic, yet, being insects, they must still breathe at the surface and—this fascinates me to no end—moult out of the water. They will leave fragile skins on my experimental enclosures later in the spring.
Though their bellies have a fragile, stained-glass appearance, their backs are startlingly white. Like many other aquatic animals, they’re blending in with the water’s surface as seen from the pond bottom, but because they swim upside down, it’s their backs instead of their bellies that are pale.
Notonectids (yes, I’m claiming friendship) are voracious. They will eat tadpoles much bigger than themselves. They will bite people who pick them up. I caught one sucking the lifeblood from an injured stickleback last summer. Be warned.
Among the seeds and snails and breathing backswimmers drift tissue-papery, cast-off skins of what I think were mosquito larvae. Before they moult into our worst nightmare, they are among the strangest of pond creatures. Picture a mosquito without wings and with are larger head. Its tail end has a breathing tube which pokes above the surface while its head hangs downwards. When it chooses to move, it bends its whole body in half and wriggles. Like many insects with an aquatic larval stage, it is hardly recognizable in this state as the flying pest it will become.
Today I saw what looked like an oversized version of said flying pest, a cranefly. Despite the unfortunately resemblance, craneflies are our allies: they eat mosquitoes, along with a huge number of other creatures from dragonflies to birds and bats. Much as I might curse the existence of mosquitoes, and even more so in places where they carry deadly diseases, it’s at least a tiny consolation that they support such a wealth of species.
Note: the promised post on frogs and fish nests is being put off until next week.
*Called water boatmen in the UK. The creatures we North Americans refer to as water boatmen are in a different but related family and swim right-side up.