Wonderful world of the whirligig
They are very strange creatures — in fact all water beetles are a bit odd. The whirligigs are those small, dark beetles that gather in clusters on the water surface and swim round in mad circles. They are predators and apparently swimming in circles is a way of locating prey. They catch things on the surface and below it so they have two pairs of eyes, one for seeing in water and one for seeing in air. The purpose of the whirling is to create ripples. If something like a midge lands on the water surface it alters the pattern of the ripples and the beetles sense this instantly and uses it to locate the prey.
If you disturb them they disappear under water. This is another neat trick because adult whirligigs, like all other water beetles, have no gills and have to breathe air. They manage this by grabbing a bubble of air in an organ at the tip of the abdomen and using it like a scuba diver’s tank. They can stay under water for a remarkably long time and, when they’re not whirling, this is where they hunt. But eventually they have to make a rapid trip to the surface and grab another bubble.
Other species of water beetle and water bugs, like water-boatmen, do the same thing. They are all strong swimmers, using long, flattened legs that look like oars. They mostly live and hunt in underwater vegetation and the moment when they dash to the surface for air is a dangerous one. It exposes them to the many species of fish that like to eat beetles. If you manage to catch a whirligig beetle it will emit a very strong smell. This is its defence mechanism, though it doesn’t seem to work very well against fish.
To add to the beetle’s list of accomplishments, it can also fly. It normally only does this once a year, at night in late summer or early autumn. It will then fly considerable distances in order to locate new canals, ponds or ditches to colonise. It can’t survive in fast-flowing water. The rather unexpected mastery of flight explains why water beetles and water-boatmen can suddenly appear, and equally suddenly disappear, in garden ponds.
The larva of the whirligig beetle looks like a totally different species. It’s long and thin with a frill of legs and filaments down each side, a bit like a centipede. The filaments are gills so the larvae, unlike the adults, don’t have to risk their lives grabbing bubbles of air from the surface. But, despite their adaptation to water, they crawl on to land and spin a cocoon when pupation time arrives.
Creatures like this fill me with wonder at the extraordinary variety of the adaptations that evolution produces.
Buttercups have a long flowering season but it’s at its height around now. The yellow flowers are very familiar, though in fact there are many species, some of which have white flowers (though always with a yellow centre) and some of which, like water crowsfoot, are aquatic plants. The three commonest native species are the meadow buttercup, growing in damp fields and road verges, the bulbous buttercup, in dry soils, including sand dunes, and the creeping buttercup, which can be a serious garden weed. The name probably comes from an old belief that it was buttercups that made butter yellow. Another old belief is that if a child presses a flower to its’ chin, leaving a yellow pollen stain, he or she is fond of butter. The Latin name is more of a mystery, it’s Ranunculus which means a little frog, and nobody seems to know why.
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