
Nepidae is a family of exclusively aquatic Heteropteran insects in the order Hemiptera. They are commonly called water scorpions for their superficial resemblance to scorpions, 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, in two subfamilies, Nepinae and Ranatrinae. Members of the genus Ranatra, the most widespread and species-rich genus, are sometimes called needle bugs or water stick insects as they are slenderer than Nepa.
Laccotrephes is a genus of water scorpion belonging to the family Nepidae. They are carnivorous insects that hunt near the water surface. They are not aggressive, but may inflict a painful bite if not handled carefully, which may cause a local reaction. There are about 60 species found in shallow stagnant or slow-moving waters in warm parts of Africa, Asia and Australia.
Laccotrephes pfeiferiae is a species of water scorpion belonging to the family Nepidae. It was until 1999 considered synonym of Laccotrephes robustus; records of L. robustus outside the Philippines refer to this species.

Nepa is a genus belonging to the family Nepidae, known as water scorpions. There are six species found in freshwater habitats in the Northern Hemisphere.

Nepa apiculata is a species of waterscorpion in the family Nepidae. It is found in eastern North America.

Nepa cinerea is a species of water scorpion (Nepidae), found in most of Europe, including the British Isles, as well as North Africa and southern and northern Asia.

Ranatra is a genus of slender predatory insects of the family Nepidae, known as water scorpions or water stick-insects. There are around 100 Ranatra species found in freshwater habitats around the world, both in warm and temperate regions, with the highest diversity in South America and Asia. Fewer are found elsewhere, but include several African, some in North America, three from Australia and three from the Palearctic, notably the relatively well-known European R. linearis.

Ranatra fusca is a water stick-insect in the family Nepidae, native to North America. It is known by the common name brown water scorpion. It is generally 3.2–4.2 cm (1.3–1.7 in) long.

Ranatra linearis is a species of aquatic bug in the Nepidae family. It is native to Eurasia and North Africa, and primarily found near aquatic plants in ponds, marshes and other freshwater habitats, but has exceptionally been recorded from hypersaline lakes and brackish lagoons.