SKITTERING WATER STRIDERS
Beijing, 17 August 2013
It was flowers in the Spring. It is insects in the high summer. Because this posting, following on from my previous two on dragonflies and crickets, will be on water striders. I began to notice them a week or so ago, on my daily crossings of my piece of canal to and from work. As is my habit, I was looking over the water to see what was new, when a sudden, evanescent dimpling of the water surface caught my eye. Then there was another, and then another … No doubt about it, the water striders were out and about, skittering across the water’s skin.
I love these insects, they are part of my childhood. During those long summer holidays which my family spent in France with my grandmother – golden-hued in my memory – I spent a lot of time with my cousins biking across the countryside. In those days, there were still a lot of lavoirs, washing stations, dotted across the countryside. They were places where the women (no men, of course …) used to come to wash the family’s clothes.
They were located along a stream. Sometimes, a basin would be built alongside the stream, fed by it and discharging back into it.
But just as often, the women washed directly in the stream; if necessary, a small dam was thrown across the stream to create a pool of still water for washing.
By the time my cousins and I were biking around, the lavoirs were hardly used any more. The march of the washing machine across the landscape was underway. But the infrastructure was still largely intact. We would often stop at the lavoirs, for a rest, to splash our faces, wash our bikes if needs be – and to watch the water striders. The pools of still water which had been created for the washerwomen were very much to the striders’ liking, so they haunted these spots. With the casual cruelty of little boys, we would take a poke at the striders, watching them skim away across the water’s surface. We were fascinated by their ability to stand on water (it’s not for nothing that another name for these insects is Jesus bugs).
I’ve been boning up on water striders, primarily to understand how it is that they can stand on water. I won’t bore you with the details, but it has to do with being light, spreading this light weight over a number of legs, and having a lot of hairs on those legs. This is enough for them not to break through the water tension. Who wouldn’t like to be able to walk on water? With our weight, we can only walk – or at least sit – on mercury.
I remember being fascinated by this photo when I saw it years ago in an article in the National Geographic on mercury. Now, with everything I know about the awful effects of mercury on people, it makes me shudder profoundly.
In passing, I’ve also learnt how water striders feed. When an insect falls into the water, the strider senses its struggles through small vibrations and ripples in the water surface. It darts across to the poor thing, pierces it, and injects saliva. The enzymes in the saliva digest the victim’s tissues. The strider then sucks up the partially digested broth.
Now that I’ve totally grossed out my wife and any other normal readers, I put in this nice close-up picture.
Water spiders: http://upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Amenbo_06f5520sx.jpg/450px-Amenbo_06f5520sx.jpg
Man floating on mercury: http://i.imgur.com/DfTbR.jpg
Water spider-closeup: http://img.burrard-lucas.com/united_kingdom/full/pond_skater.jpg