I found this beetle in my small garden pond and made some pictures (slides) of
it. Not knowing then this would render a new impulse to my "ditch photography"
passion, ending in spending a lot of time on this website.
By the grooves in the wing cases (elytra) you can recognise the female of the Great
diving beetle. The males have smooth elytra and broadened front legs with sucking discs.
Sometimes female specimen are found with smooth elytra, but never with sucking discs. Dytiscus
marginalis is one of the largest beetles in the Northern hemisphere (and part of the Southern
as well). It is a hungry carnivore that will bite in anything that is or was an animal.
Despite that (or thanks to?) it is an interesting creature that can be easily held separate
for a few days in a tank that is not to small. For food it will accept rainworms, flies,
maggots, cat feed, etc. The Great diving beetle is often scooped out of garden ponds to be
killed, because they may damage goldfish or other expensive fishes. That really is pity,
because in the last era it's natural habitats are almost completely destroyed. So it's
better to carry them over in a ditch nearby, or simply let them fly away. You could consider
creating a small, more natural pond in your garden. Then you might learn that the frogs, newts
and beetles that come to visit it, are much more interesting then those eternal goldfish...