Friday, February 18, 2011

Great Diving Beetle

While cleaning out my Water Butt at the back of the Greenhouse this morning, I came across three Great Diving Beetles at the bottom of the Barrel.  The Great Diving Beetle Dytiscus marginalis is one of our largest beetles. This species has a dark, olive-brown, almond-shaped oval body, about three centimetres long, with the thorax bordered by dull yellow. The males have suction discs on the front feet for gripping the female while mating and smooth wing cases, on which the females have deep groves. This beetle is very common in weedy, standing or slow-flowing water and is often found in garden ponds. The three beetle in my barrel probably came from the lake in from of my house.


Great Diving Beetle male
Great Diving Beetle female
Great diving Beetle male & female

Great Diving Beetles periodically come to the surface, extruding the tip of the abdomen to replenish an air supply kept under the wings. This species will sometimes fly to outside lights at night. They are able to leave the water and fly off to colonise new ponds, sometimes landing in error on shiny car roofs or cold-frames in mistake for a water surface!   My Greenhouse must have attracted these beetles as they were flying around at night, from where they dropped onto the glass and then into the water gutters and ended up washed into the water butt.

Great Diving Beetle male
Great diving Beetle female
Great Diving Beetle male
Great Diving Beetle male & female

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