Thursday, 5 September 2013

The pond skater's lunch

There may not be much open water in the early autumn warmth but where the ponds stay wet life and death goes on. Pond skaters are very conspicuous right now. These are members of the true bugs, the Hemiptera, with sucking mouthparts drawn out into a stiletto-like proboscis, all the better for sucking the juices out of hapless victims. Watch the pond skaters for a while, there is an elegance and simplicity to their movement, a single stroke of those long pairs of legs is enough to catapult them across the water, then, propped on their cantilevered second and third pairs of legs, wait perfectly still on the surface. They are skittish, slightly nervous creatures when fully grown, as in the picture. Newly hatched young in mid-summer are pin-pricks perched on tiny cross hair legs.

Their fidgety nature hides a murderous intent. These are predators, specialising in other insects trapped in the surface film. The skaters’ impressive water geometry is a patrol in search of prey. They react to the vibrations of water logged wings or twitching legs by sidling up, ever so nonchalantly, inspecting their target for signs of danger. Then, if they sense no risk, they move in for the kills. Once a prey item has been stabbed they find a raft or bankside refuge to which they  retreat and enjoy their meal.  Sometimes several skaters home in on one victim, resulting in a flurry of skips and hops, legs seeming to go all over the place as they jostle for position. The skater in the picture has harpooned a Bibionidae fly, and there are other flies and a frog hopper mired in the surface tension nearby, as well as smaller flies perched on the water surface in search of their own, tiny prey. The skater is using the feather as a platform on which to finish its meal. Stylish, but deadly

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