Sunday, 13 May 2012

Water Strider's competition

The gauntlet has been thrown between Mark (Beating the Bounds) and myself in photographing Water Strider’s (Gerridae), so I’ve been taking more notice of them, it was only yesterday 12-5-12 that I realised how the distinctive  shadow of them is produced
(the shadow's here of only the back two feet, normaly four shadows, and the body shadow)
 the dots being the surface tension depressions of it's feet
and from Wiki :-
Water striders are able to walk on top of water due to a combination of several factors. Water striders use the high surface tension of water and long, hydrophobic legs to help them stay above water. Water molecules are polar and this causes them to attract to each other. The attractive nature results in the formation of a film-like layer at the top of water. This top layer has gravity acting downward in addition to the water molecules below pulling down the upper molecules. This combination creates a touch surface tension.

Gerridae species use this surface tension to their advantage through their highly adapted legs and distributed weight. The legs of a water strider are long and slender, providing the weight of the water strider body to be distributed over a much larger surface area. The legs are strong, but have flexibility that allows the water striders to keep their weight evenly distributed and flow with the water movement. Hydrofuge hairs line the body surface of the water strider. There are several thousand hairs per square millimeter, providing the water strider with a hydrofuge body that prevents wetting from waves, rain, or spray, which could inhibit their ability to keep their entire body above the water surface if the water stuck and weighed down the body. This position of keeping the majority of the body above the water surface is called an epipleustonic position, which is a defining characteristic of water striders. If the body of the water strider were to accidentally become submerged, for instance by a large wave, the tiny hairs would trap air. Tiny air bubbles throughout the body act as buoyancy to bring the water strider to the surface again, while also providing air bubbles to breathe from underwater.

The tiny hairs on the legs provide both a hydrophobic surface as well as a larger surface area to spread their weight over the water. The middle legs used for rowing have particularly well developed fringe hairs on the tibia and tarsus to help increase movement through the ability to thrust. The hind pair of legs are used for steering  When the rowing stroke begins, the middle tarsi of Gerrids are quickly pressed down and backwards to create a circular surface wave in which the crest can be used to propel a forward thrust. The semicircular wave created is essential to the ability of the water strider to move rapidly since it acts as a counteracting force to push against. As a result, water striders often move at 1 meter per second or faster

gauntlet passed back - cheers Danny

here's some from my earlier posts

I don't have Mark's e-mail so if you read this is it OK to post your photo's here as well ?

Thanks Mark, I think you deserve bonus points for having fish in focus as well 

 and again for catching it having dinner, and the feet indents in the surface skin


  1. That's fine with me Danny - although this is clearly a competition I'm losing hands-down.

  2. Oops -
    Now the competition has really hotted up. (No thanks to me).

    1. can't compete with Cabinet of Curiosities, it's on my Blog reading list, but he is a Professional!
      cheers Danny