In the shadow of enormous white satellite dishes and flickering wind turbines, I am lying on my stomach over a pond, my nose almost touching the muddy water below. Perhaps unsurprisingly, some passing ramblers want to know what on Earth I am doing. What I am meant to be doing is a survey - recording the land cover at a particular GPS referenced point, somewhere in the middle of Goonhilly Downs on the Lizard Peninsula in Cornwall. But, I got distracted.
I couldn’t pass by this tiny pool without stopping. Surrounded by ghostly pale orchids and yellow spikes of bog asphodel, it is brimming with life. Common blue damselflies perch delicately on the scrubby pond-side willow, whilst all around me, their larger, more aggressive relatives, the gold ringed dragonflies and broad-bodied chasers, buzz and collide with a zzzpp. I got down onto the ground in order to photograph a newt - a male palmate, with black, conspicuously webbed back feet – but the camera couldn’t focus on it in the murky water. Once I was down there though, I noticed the water boatmen steadily rowing through the water and became mesmerised by the whirligig beetles, which carved crazed circles on the surface, like cars on a Scalextric track.
These tiny beetles live life on the edge, at the interface between air and water. As I watch, they hunt for small invertebrates trapped on the meniscus, using a form of echo-location to find their way. The waves they create in front of them are reflected from obstacles and sensed by their antennae, allowing them to detect their prey. But, whirligigs aren’t restricted to just the surface. They have a divided eye; the top half allows them to see in the air, and the bottom half allows them to see underwater. This means that they can hunt below the surface too, taking a silvery bubble of air with them when they dive.
The ramblers have become interested in the whirligigs and as I haul myself to my feet, thinking that I should really be getting back to work, they are readying their own cameras and taking my place on the bank of the pond.
Now you do it
Whirligig beetles are common in all types of still water in Britain. There is more than meets the eye to these creatures, so why not temporarily transfer them to a jam jar or tray and study them with a hand lens? See if you can see their orange legs and divided compound eye. ARKive has amazing close-up videos of whirligigs (much better than mine!).
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