The Genus Stenus

Posted by Graeme Lyons , Wednesday, 28 September 2011 18:53

Whilst sampling aquatic invertebrates yesterday at Woods Mill I spotted a small rove beetle in the tray and thought I would attempt to identify it. There are more species of rove beetles in the UK than there are macro moths, over a thousand! This is around a quarter of all beetles so I can't ignore them forever. I bought the key to Staphylinidae by Derek Lott and Roy Anderson in the summer but have not really used it much. The beetle I found yesterday is clearly in the genus Stenus, of which there are 74 species!

It did key out quite easily though and I managed to get it to species, Stenus solutus. I read a little more into the natural history of the genus and discovered something quite remarkable. As these species live by water, they have an adaptation for getting back into emergent vegetation. They land on the surface tension of the water and secrete a strong detergent. This reduces the surface tension at one end of the beetle, producing a net force in the direction they wish to travel. How cool is that?!

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