Long-button water beetle
| Long-button water beetle | ||||||||||||
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Long-button water beetle |
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| Mulsant , 1844 |
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The long-headed water beetles (Hydraenidae) are a family of beetles that were previously taxonomically placed in the family of the piston water beetles (Hydrophilidae). Over 400 species have been described worldwide, including 90 species in Central Europe and 52 species in Germany.
anatomy
The long-button water beetles are small, one to five millimeters long, dark to ocher-brown in color, elongated animals that predominantly live in water. They have slightly longer antennae than the piston water beetles and since they cannot swim, but rather crawl around in the water, they lack the characteristic shape of swimming beetles. The body outline is more articulated than closed. In the Limnebius species, the end of the wing-covers are truncated across so that the end of the body is exposed. The strongly elongated maxillary palps , hence long- button water beetles, serve as tactile organs . As with the water beetles, these have partially taken over the antenna function.
habitat
The Hydraenidae are strictly specialized in their choice of biotope. So animals of the genus Hydraena and some species of the genus Ochthebius are represented in flowing waters. Other representatives of the genus Ochthebius (Germany = O. dilatatus ) can be found in the coastal area ( brackish water , riparian zones, splash ponds - with often considerable salinity). The Limnebius species prefer standing or flowing small bodies of water. The aquatic animals feed on unicellular algae as larvae and as imago , whereas the terrestrial animals feed on organic detritus .
Way of life
Like the water beetle, all species have a thin, almost incompressible air jacket (plastron) on the belly side, which stretches between highly water-repellent cuticular hairs on the body surface (also in other water beetle families), is connected to the tracheal system via stigmas and its carriers as physical The gill is used which, in contrast to the simple air bubble that adheres to the body, does not need to be renewed. As with the Hydrophilidae, the breathing air is supplied via the antennae, which with their hairy club establish contact between the plastron and the atmospheric air.
Reproduction
For their individually deposited eggs, some species use their spinnerets to create a loose, webbing shell. To pupate , the larvae go ashore and spend the pupal time in cocoon-like or hemispherical housings above the waterline. Some species spend their entire larval time on land, only to remain in the water as beetles after pupal rest .
literature
- Bernhard Klausnitzer : Beetles in and around the water. 2nd, revised edition. The new Brehm library, Volume 567. Westarp Sciences and Spectrum, Academic Publishing House, Magdeburg, Heidelberg, Berlin and Oxford 1996, ISBN 3-89432-478-3
