What is "water scorpion"

Nepa \Ne"pa\, n. [L. nepa scorpion.] (Zo["o]l.) A genus of aquatic hemipterous insects. The species feed upon other insects and are noted for their voracity; -- called also scorpion bug and water scorpion.

n. Any long-legged aquatic insect of the family ''(taxlink Nepidae family noshow=1)'', especially the species (taxlink Nepa cinerea species noshow=1).

n. long-legged aquatic insect having the front legs fitted for seizing and holding prey and the abdomen extended by a long breathing tube