Thomisus onustus
| Thomisus onustus | ||||||||||||
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Thomisus onustus |
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| Scientific name | ||||||||||||
| Thomisus onustus | ||||||||||||
| Walckenaer , 1805 |
Thomisus onustus is a species of spider from the family of the crab spiders (Thomisidae) and in Europe the only species of the genus Thomisus . It ispatchy and not commonin Central Europe .
features
The species is unmistakable in Central Europe due to the pointed rear corners of the rear body ( opisthosoma ) and the lateral eyes that protrude to the right and left of the front body ( prosoma ).
Thomisus onustus is one of the large crab spiders in Central Europe. However, this only applies to the females, because the species shows an extreme sexual dimorphism in terms of size and color, which is even larger than that of the similar variable crab spider . Males only reach a body length of 2.0-3.6 mm, while the females are 7.0-9.8 mm long. The male has a monochrome yellow-brown to dark-brown front body ( prosoma ); the back of the body ( opisthosoma ) is also monochrome and yellow-green to brownish. The two front pairs of legs are broadly ringed in light brown and reddish brown, the two rear pairs of legs are monochrome, light beige. Females are very variable in color, the basic color of the entire body can be white, yellow or pink. The animals can be completely monochrome, but yellow or pink stripes on the opisthosoma and pink or reddish ringlets on the legs are common in yellow or white animals. Pink-colored animals often show a broad, dark-gray-rimmed prosoma and white spots on the opisthosoma as well as dark-gray-ringed legs.
distribution and habitat
The huge range of Thomisus onustus covers large parts of the Old World from Great Britain and Portugal in the west to Japan in the east. In the north-south direction, the distribution extends from Sweden to South Africa and in the east from Central Siberia to Java . The distribution area includes the temperate to tropical zone. Thomisus onustus occurs in almost all of Europe, but the distribution becomes increasingly patchy towards the north. It is absent in Iceland and Ireland, as well as in Norway , Denmark and Finland . In Germany, the species is only sparsely distributed and is rarely found. The occurrences are essentially limited to the heat-favored areas in the south-west and north-east.
The species is extremely warmth-loving. It colonizes forest-free and very dry habitats with high levels of solar radiation, especially sandy dry grass and semi-dry grass and very sparsely overgrown, young fallow land.
nutrition
To catch prey, the species hangs on flowers of free-standing plants. The females, like the mutable crab spider, are able to adapt the body color to the respective flower color. The prey consists of all kinds of flower-visiting insects, e.g. B. hover flies , bees , wasps , butterflies or smaller beetles , which are often several times larger than the spider. This seizes its prey with lightning speed with the two strong and greatly enlarged pairs of forelegs and usually kills it with a bite in the rear neck.
Reproduction
Mating occurs mainly in June. Similar to the mutable crab spider, when a male has found a female, it climbs on its back. For copulation, however, it climbs to one side of the opisthosoma and from there introduces a pedipalp into the genital opening of the female in order to then switch to the other side of the opisthosoma. This position is considered to be more primal than the belly-to-belly position of most other crab spiders. The male then climbs back onto the female's back and then copulates again after a pause. Eventually the male leaves the female. The female is completely passive towards the male during the entire mating process and shows no aggression.
Danger
Thomisus onustus is classified in Germany as "endangered" (category 3) in the Red List due to its rarity and its close connection to heat-exposed, sparsely vegetated open areas. Regional, e.g. B. in Berlin , the species is considered "critically endangered."
swell
literature
- Heiko Bellmann : Cosmos Atlas Arachnids of Europe . 3rd edition, 2006. Kosmos, Stuttgart, ISBN 978-3-440-10746-1 .
- Ralph Platen, Bodo von Broen, Andreas Herrmann, Ulrich M. Ratschker, Peter Sacher: Total species list and red list of spiders, harvestmen and pseudoscorpions of the state of Brandenburg (Arachnida: Araneae, Opiliones, Pseudoscorpiones) with information on frequency and ecology. Nature conservation and landscape management in Brandenburg 8, booklet 2 (supplement); 1999.
Individual evidence
- ^ Map on the worldwide distribution of Thomisus onustus from the British Arachnological Society
- ^ Atlas of the arachnids of Europe: Evidence from Thomisus onustus
Web links
Thomisus onustus in the World Spider Catalog
- W. Nentwig, A. Hänggi, C. Kropf & T. Blick (Eds.): Spinnen Mitteleuropas - Identification key, genus Thomisus. on-line