Monday, 9 July 2012


Following on from our aborted walk around 'Swan Lake' the other day, here is a picture of a nasty-looking creature which we found struggling along a dry part of the path.  at the time, I thought it was a Dragonfly nymph of some sort, but on closer inspection, it turns out to be the nymph of a Great Diving Beetle (Dytiscus marginalis).
At about three inches long and sporting an enormous pair of jaws, it made a formidable image as it inched its way along. Not wanting to risk a nip from those jaws, I picked it up on a large leaf and transported it back to the water where I managed to take its picture before it swam into the vegetation. The jaws are used to great effect when it hunts its prey. They are sunk into the unfortunate prey item like hypodermic needles, while it injects a digestive enzyme. The resulting 'soup' is then sucked up by the nymph. They will eat anything they can get their jaws into. Tadpoles are their favourites, but they will tackle small fish and even turn to cannibalism. They breathe through a spiracle (or air hole) at the end of the tail as can be seen from the photo above and will often be seen with the tail breaking the surface of the water, taking the air.
We will have to keep a look-out for the stunning adult beetle in the lake when the water has gone down a bit.
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