Nepidae

Definition

A family of aquatic true bugs (Hemiptera: Heteroptera: Nepomorpha) commonly called water scorpions, characterized by raptorial forelegs adapted for seizing prey and a long, slender respiratory siphon extending from the posterior abdomen that functions as a snorkel while the insect remains submerged. The family comprises approximately 270 species in 14 genera divided between two subfamilies: Nepinae (broad-bodied water scorpions including Nepa) and Ranatrinae (slender water stick insects including Ranatra).

Etymology

From Nepa (type genus, Latin for a type of aquatic bug) + -idae (family suffix).

Example

Nepa cinerea, a European member of Nepidae, lies motionless among submerged vegetation with its caudal siphon projecting to the surface; when prey such as tadpoles or small fish approach, the bug strikes with its grasping forelegs and injects digestive enzymes through its piercing-sucking rostrum.

Synonyms

• water scorpion family

Related Terms

• Nepomorpha
• Heteroptera
• Nepa
• Ranatra
• caudal siphon
• raptorial foreleg
• Nepinae
• Ranatrinae
• Belostomatidae
• Notonectidae

Usage Notes

The common name 'water scorpion' refers only to superficial resemblance in body form and raptorial appendages; Nepidae are true bugs, not scorpions or arachnids. Distinguish from slender Ranatrinae (often called water stick insects or needle bugs) and broad-bodied Nepinae. The caudal siphon is a respiratory structure, not a stinger—despite the common name, Nepidae cannot envenomate vertebrates. In ecological studies, Nepidae serve as useful indicators of permanent, vegetation-rich freshwater habitats.