Subject matter of experiments and observations of water animals in school aquarium X (Water scorpions)
Abstract
Rearing of two species of water scorpions (Heteroptera, Nepidae) in school aquaria is described in this contribution. The body of water scorpions is cylindrical (Ranatra linearis) or flattened (Nepa cinerea) with a siphon to pierce the water surface for air.
Their bodies resemble stick or leaves allowing them to remain motionless as sit-and-wait predators along pond or streams margins waiting for prey to come within reach of their mantid-like forelegs. They are poor swimmers, but able to propel themselves with jerky leg motions.
The body of Ranatra linearis is brown, typically 30-40 mm long. Their breathing tube tail is usually about as long as the body of the insect.
The adults can fly. Stridulations and vibrations were reported for the forelegs of Ranatra with a femoral plectrum and coxal pars stridens.
Nepa cinerea lives like Ranatra linearis, in ponds, small rivers, stagnant water, canals, and wetlands with aquatic plants and plant debris. It feeds upon aquatic animals, especially insects.
Nepa cinerea is blackish brown in colour and measures about 12-23 millimetres. On molestations, Nepa and Ranatra show thanatosis; they can a long time stay motionless.
Bites of both Nepa and Ranatra are painful for humans. Some experiments and observations suitable for school aquaria are suggested (e.g., habitat preference, food behaviour, thanatosis, reaction to light).