
Great diving beetle larva
Definitely one of the most voracious killers in a pond. They will eat everything that moves. For this picture i caught two of them and put them in my small 'photo aquarium' but sadly after a few minutes i only had this one (the smaller one) left with a body that suddenly was not so transparent anymore, and also a lot bigger. At least he had a good dinner before returning to the pond! :)

The great diving beetle, Dytiscus marginalis, is a large aquatic diving beetle native to Europe and northern Asia, and is particularly common in England. The great diving beetle, true to its name, is a rather sizable insect. The larvae can grow up to 60 millimetres (2.4 in) in length, while the adults are generally between 27–35 millimetres.