Hydraenidae

Long- button water-beetles

Long- button water-beetles ( Hydraenidae ) are a family of beetles that used taxonomically in the family of water beetle ( Hydrophilidae ) were asked. Worldwide, more than 400 species are described, of which about 90 species in Central Europe and in Germany 52 species.

Physique

Long- button water beetles are small, one to five millimeters long, dark ocher to brownish, oblong, mainly aquatic wildlife. They have slightly longer probe than the water beetle and since they can not swim, but rather crawl about in the water, they lack the characteristic shape of water beetles. The body outline is rather organized as closed. The Limnebius species the elytra are truncated cross at the end, so that the end of the body is exposed. As tactile organs serve the highly elongated Maxillarpalpen, so long button - water beetles). These have partly taken the antenna function as the water beetles.

Habitat

In the habitat choice Hydraenidae are strictly specialized. Thus animals of the Hydraena and some species of the genus Ochthebius are represented in rivers. Other members of the genus Ochthebius ( Germany = O. dilatatus ) are in the coastal zone ( brackish water, riparian zones, splash pools - often with considerable salinity) to find. The Limnebius species prefer still or flowing ponds. The aquatic animals feed as a larva and as an imago of unicellular algae, terrestrial contrast of organic detritus.

Way of life

As the water beetle have all kinds on the ventral side of a thin, nearly incompressible air jacket ( plastron ), who stretches between highly water repellent cuticular hairs on the body surface ( in other water beetle families ), is connected to the tracheal system connected via spiracles and its makers as physical Gill serves that need to be in contrast to the simple, adhering to the body bubble, not renewed. The breathing air supply, as in all the Hydrophilidae on the sensor, making contact between plastron and atmospheric air with her hairy leg.

Reproduction

Provide for their single eggs laid some species with their silk glands a loose cocoon shell forth. For pupation the larvae go ashore and spend the time in cocoon-like dolls, or hemispherical housings above the waterline. Some species spend their entire larval period ashore, only to remain after pupation as a bug in the water.