All winter the ditches beside the forest track flowed with water draining from the hillside. Today, after a fortnight of drier weather, they were reduced to small pools as smooth as mirrors; perfect for the water crickets that had come to skate on their surface.
I knelt down, intent on catching one of these insects in the plastic specimen tube I always carry in my pocket. My plan was to submerge it behind the bug, which would be swept into the container with the inrush of water. It took a dozen attempts.
Water crickets, Velia caprai, have excellent rearward vision, a good turn of speed and can jump. And when danger threatens they use their mouthparts to spit saliva backwards between their legs, lowering the surface tension behind so that they are rapidly dragged forward by the shrinking elastic meniscus in front.
Water crickets lead extraordinary lives. They are members of a highly specialised fauna known as the epineuston, a select fellowship that can walk on water. Fully grown they are only about 8mm long, but under a hand lens I could see dimples in the surface film made by six minutely hairy feet, with two front legs held mantis-like for catching prey, two hind limbs for steering, and a middle pair acting as oars.
A life supported by surface tension gives water crickets a sensory outlook that can only be imagined. Ripples spreading from struggling prey trapped by the cohesive forces of water molecules under their feet guide these predators to their victims, but waves propagated from their own movements are also detected by fellow water crickets sharing the pool.
How do they distinguish between conflicting signals transmitted across a world that wobbles under their feet? Can they modulate their own wavelengths to communicate with each other? They are small and commonplace but full of mysteries. Next time I’ll take a tuning fork, to see how they respond to its waves.
I lowered the tube back into the pool. My captive floated motionless for a moment, then scooted away across a confusion of ripples emanating from a melee of water crickets that seemed to be engaged in rough and tumble courtship.
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