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Taking it in your stride

April 8, 2016

On many a sunny afternoon have I sat by the dam watching the passing parade of insects – dragonflies on the prowl for food, wasps digging up mud to build nests and flotillas of water striders cruising on the surface. Of the three, the latter seem the most ‘chilled’ and I often wondered what goes through their minds as they float about. Well the answer is sex and food.

water strider DSCN4211-002Water Striders are of the order Hemiptera, true bugs with sucking mouthparts. This order includes gumtree hoppers, psyllids and cicadas. These three insects use their mouthparts to suck sap from leaves. The water striders however are voracious predators, feeding on insects and spiders. They detect prey that has fallen in the water by ripples made on the surface. The small front legs are used to grasp prey and then with their mouthparts they pierce the victim, inject enzymes which dissolve it and then suck up the resultant liquid. The photo (above) shows a water strider surrounded by, if you look closely, the husks of several victims.

water striderDSCN6918The ability of water striders to remain on the water surface is a result of several factors. Hydrogen bonding between water molecules creates a surface tension. In addition thousands of tiny hairs on the feet of water striders repel water. The wide stance of the legs means the body weight is spread over a wide area. The combination of these factors means that water striders can stay afloat, even in choppy surface conditions using the middle pair of legs to propel themselves and the back pair of legs to steer.

During mating season water striders do not associate in communal groups. Territories are aggressively defended by male striders and potential mates are attracted by creating ripples on the water surface. After mating the female insect is ‘protected’ so that no other male can mate with them. The photo (above right) shows two mating pairs of water striders feasting on a honey bee…sex and food simultaneously.

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