1) Arthropod family 2) Family dytiscidae 3) Water beetles 
Dytiscidae is the predacious diving beetle family of insects of the order Coleoptera, with over 100 species found in Britain. They have modified hind- legs adapted for use as paddles and covered with long hairs and a streamlined body. They are excellent at flying and can move to new water as required. They carry air beneath the elytra, and use this...
[n] - water beetles
family Dytiscidae noun water beetles