SUBJECT MATTERS OF EXPERIMENTS AND OBSERVATIONS OF WATER ANIMALS IN SCHOOL AQUARIUM VIII (REARING OF GREAT SILVER WATER BEETLE AND RELATIVE SPECIES)
Abstract
Great silver water beetle (Hydrophilus piceus) is the largest beetle of aquatic beetles in the world. Adults can reach up to 5 cm.
The common name of Silver Water Beetles refers to the appearance of the underside which is covered by hairs, when submerged, is covered with a layer of air (known as physical gills). All species swim with alternating leg movements and carry air beneath the elytra which they renew by surfacing head first.
The adults are in general detritivores or herbivores but will also feed on worms etc. while the larvae are predatory upon aquatic animals. They occur in a wide variety of aquatic habitats but in general inhabit well vegetated standing or slow-running and shallow waters; they fly well and come to light or will alight on illuminated surfaces, sometimes far from water.
Adults are long-lived, up to 2 or 3 years, and generally leave the water to overwinter among marginal vegetation or in soil. Oviposition occurs in the spring; the females use structures similar to arachnid spinnerets to produce egg cocoons which are generally placed among marginal vegetation or left to float.
The larvae are aquatic but when fully grown leave the water to pupate among marginal soil and have occasionally be found far from the water area. In this contribution some observation in school aquaria are presented.
Breeding of hydrophilid beetle is well known and the earliest mention of the breeding of the Silver Water Beetle in an aquarium dates back to the mid-19th century. In aquarium tanks can be kept also similar water scavenger beetle Hydrophilus aterrimus, or smaller species (Hydrochara flavipes or H. caraboides) reaching less than 2 cm of their body length.