1) Arthropod family 2) Family nepidae 
Nepidae is a family of exclusively aquatic Heteropteran insects in the order Hemiptera. They are commonly called waterscorpions for their superficial resemblance to scorpions, which is due to their raptorial forelegs and the presence of a long slender process at the posterior end of the abdomen, resembling a tail. There are 14 genera in the family...
The Nepidae are the water-scorpions. They are aquatic, insectivorous Hydrocores with three or four jointed antennae and a body flat above and elliptic below. The fore legs are raptorial, the rest simple, fringed or flattened and used for swimming.
[n] - water scorpions
family Nepidae noun water scorpions