Hydroscaphidae
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| Le Conte , 1874 |
The Hydroscaphidae are a family of the beetles (Coleoptera). Thirteen species in three genera are known worldwide, two of which live in Europe .
features
Beetle
The beetles are one to two millimeters long. Their body is spindle-shaped (fusiform) and tapers towards the end of the abdomen, which, as with the tumbler beetles (Gyrinidae), is not covered by the winglets . Their bodies are dark in color, smooth and covered with very fine hairs. The broad and short head is large in relation to the rest of the body. The compound eyes are large and do not protrude, but are embedded in the side edge of the head. The antennae are about so long that they reach the rear edge of the sternum on the prothorax . They are five-membered in the genus Scaphydra , otherwise eight-membered. The last segment of the antennae is thickened like a club. The prothorax is short, the wings are shortened and truncated at the back. They only cover the first to third or first to fourth tergites of the abdomen. The tarsi are tripartite. The abdomen has six visible ventricles on the third to eighth segment. It tapers sharply towards the end of the abdomen. The second to fourth tergite is characteristically hairy, the segments five to eight are very mobile. The tergites and sternites on the fifth to eighth abdominal segment are laterally fused so that they form a sclerotized ring. The last, eighth sternite is pointed at the back.
Larvae
The pre-imaginal stages of the genus Yara are so far unknown. The larvae of the other two genera, like the adults, have a spindle-shaped body that is broad in front and tapering to a point at the back. The tergites are hairy on the sides. The head is wider than it is long, has five point eyes ( ocelli ) and has partly forward-facing mouthparts. The antennae are two-part and very short. The pronotum has toothed scales. The legs have very strong, simple claws with two flattened spurs at the base. The tergites on the thorax and the first to seventh tergites on the abdomen have rows of lanceolate hairs on the rear edge.
Doll
The pupation occurs as covered doll (Pupa obtecta), which in the Exuvie remains the last larva. Only the rear part of the thorax and the base of the abdomen are visible after the larval skin has broken open. These parts are more sclerotized than the invisible ones. Functional tracheas or tracheal gills are formed on the first to third abdominal segments .
Occurrence and habitat
The genus Hydroscapha is distributed in western North America, Mexico, Eurasia, North Africa, Southeast Asia and Madagascar, the genus Scaphydra occurs in southeastern Brazil and the genus Yara in Brazil and Panama.
Both the larvae and the adults are common in rivers and streams on algae that are covered with a thin film of water. They can be very numerous in ideal habitats. The animals apparently prefer fast-flowing and oxygen-rich waters, but can occur in different habitats. Occasionally, the beetles can be found on the sandy edge of bodies of water, Yara vanini is regularly found in periodic watercourses and was first discovered in damp mud. However, the species has also been found in stony areas and on moss pads and algae in rapids. The adults of Hydroscapha can occasionally be found under stones in fast-flowing waters to a depth of one meter in the ground. The Hydroscaphidae colonize bodies of water with a wide range of temperatures. They can be found in hot springs, such as in Arizona, and in cold waters, such as the Amargosa River in Nevada.
Way of life
As far as is known so far, larvae and adults feed on algae. Little is known about the development of animals. The females of Hydroscapha only lay one large egg at a time. Pupation takes place in the water in which the last larval molt took place. The beetles also spread by flying, which has been proven by findings in swimming pools.
Taxonomy and systematics
The family is characterized by the spindle-shaped body with a broad head and thorax and a clearly tapering abdomen in both the larvae and the adults. The adults differ from the other beetle families by their ring-shaped sclerotized, highly mobile fifth to eighth abdominal segments and the characteristic adjacent hairs on the third and fourth abdominal sterngith. The two genera Scaphydra and Yara are related to each other in a sister relationship , which is justified by the forked apophysis with an elongated shaft, which turns at the basal thickening of the aedeagus . Two types of the family are known from Europe:
- Hydroscapha crotchi Sharp, 1874
- Hydroscapha granulum (Motschulsky, 1855)
Individual evidence
- ↑ a b c d e f g h Rolf G. Beutel, Richard AB Leschen: Handbuch der Zoologie - Coleoptera, Beetles, Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim) . 1st edition. de Gruyter , 2005, ISBN 3-11-017130-9 , p. 49 ff . (English).
- ↑ a b Hydroscaphidae. Fauna Europaea, accessed April 20, 2010 .
literature
- Rolf G. Beutel, Richard AB Leschen: Handbuch der Zoologie - Coleoptera, Beetles, Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim) . 1st edition. de Gruyter , 2005, ISBN 3-11-017130-9 (English).
