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Nepa cinerea01.jpg
Nepa cinerea
Ranatra elongata.png
Ranatra elongata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Suborder: Heteroptera
Infraorder: Nepomorpha
Family: Nepidae
Subfamilies, Genera

See text

Nepidae is a family of exclusively aquatic Heteropteran insects in the order Hemiptera.[1] They are commonly called waterscorpions 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, and they can be found on all continents except Antarctica. Members of the genus Ranatra, the most widespread and speciose genus, are sometimes called needle bugs or water stick insects as they are more slender than Nepa.[2]


They feed primarily on other aquatic invertebrates, but occasionally take small fish or tadpoles. Respiration in the adult is achieved by means of the caudal process, which consists of a pair of half-tubes capable of being locked together to form a siphon by which air is conducted to the tracheae at the apex of the abdomen when the tip of the tube is thrust above the surface of the water. In immature forms the siphon is often underdeveloped and respiration takes place through six pairs of abdominal spiracles. The eggs, which are laid above the waterline in mud, decomposing vegetation, the stems of plants or rotting wood, are supplied with air by filamentous processes which vary in number among the genera.[2]

Subfamilies and genera[edit]

Nepidae has 14 genera divided into two subfamilies, Nepinae and Ranatrinae. Species in the subfamily Nepinae tend to have a broad, flat body measuring over two inches in length, whereas those in the subfamily Ranatrinae tend to have a long and narrow body, with similarly long and slender legs.[2]

Subfamily Ranatrinae

Subfamily Nepinae

See also[edit]

  • Eurypterid – unrelated arachnids that are commonly called ′Sea Scorpions′


  1. ^ Nepidae, Tree of life project
  2. ^ a b c I. Lansbury (1974). "A new genus of Nepidae from Australia with a revised classification of the family (Hemiptera: Heteroptera)". Australian Journal of Entomology. 13 (3): 219–227. doi:10.1111/j.1440-6055.1974.tb02176.x. 

Public Domain This article incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Nepidae". Encyclopædia Britannica (11th ed.). Cambridge University Press. 

External links[edit]