Cave wheel web spiders

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Cave wheel web spiders
Large cave spider (Meta menardi), female

Large cave spider ( Meta menardi ), female

Systematics
Class : Arachnids (arachnida)
Order : Spiders (Araneae)
Subordination : Real spiders (Araneomorphae)
Partial order : Entelegynae
Family : Extender spiders (Tetragnathidae)
Genre : Cave wheel web spiders
Scientific name
Meta
CL Koch , 1836

The cave wheel web spiders ( Meta ) are a genus of real spiders from the family of the extensor spiders (Tetragnathidae) with worldwide distribution and comprises 26 species . (As of June 2020) The best known species is the large cave spider ( M. menardi ) , which is also sometimes referred to as the cave wheel web spider .

features

Male of Meta reticuloides

The genus is not delimited uniformly, it is differentiated from some closely related genera primarily on the basis of the mating organs, the epigyne of the female and the male pedipalpus . It includes medium-sized species (in Europe from 8 to 17 millimeters in length) that build wheel nets in which the hub of the circular network is open. The base member of the Chelicerae is not remarkably long and strong in the cave wheel web spiders (and the closely related genus the autumn spiders ( Metellina )), as in the other species of the family, so that the name assignment "thick jaw spiders", or scientifically Tetra-Gnathidae (i.e. with "Four pines") does not actually apply to them; the genus was not assigned to this family until the 1980s, but was classified in the Araneidae or in a separate family Metidae. The labium appears swollen at the front (distal) end and is pale in color here. The sternum (abdominal plate) of the front body is smooth, without point pits. The abdomen (Opisthosoma) is rounded, not elongated as in the genus Tetragnatha . In contrast to the thick jaw spiders ( Pachygnatha ), the legs are clearly and richly spiked. In addition, the thick-jawed spiders no longer lay fishing nets in their adult stage. The femora (thighs) of the legs of the cave wheel web spiders do not have trichobothrium . From the autumn spiders, whose species are on average somewhat smaller, the genus can only be differentiated on the basis of the mating organs: The epigyne of the female, the paracymbium and the embolus (components of the pedipalpus) are more strongly sclerotized in the cave-wheel-web spiders. In addition, the embolus is not hidden by a conductor, the dorsal part of the paracymbium is very wide and lobed at the end. The opening of the epigyne in the cave-wheel-web spiders is more towards the rear, in Metellina it is directed downwards (ventrally), when viewed from below the epigyne is therefore formed with a wide pit in the cave-wheel-web spiders and with a central plate in the autumn spiders.

Area, way of life and habitat

Female of the southern cave spider ( Meta bourneti ) with an egg cocoon

The genus is distributed worldwide and occurs on all continents with the exception of Antarctica. Most species have a special bond with caves as a habitat, so they are cave-loving or troglophilous; but this does not apply to all species. However, they usually do not live deep inside the cave, but rather in the zone of twilight near the cave entrance. From there they are also into man-made habitats such as tunnels, cellars, bridges and the like. passed over. They are ambulance hunters who steal their prey with the help of bicycle nets, but sometimes they actively leave the net and hunt freely on the cave walls. The females of the European species lay a few centimeters long, round cocoon hung on a strand of thread for their eggs, which is guarded by the female. The hatched young spiders only leave it in the spring of the following year. Sometimes they go to the cave exit, where they can fly off with the help of a long silk thread released into the air (called " ballooning ") and thus colonize new habitats through long-distance distribution. You may recognize this by the cool draft of air out of the opening. The way of life of most of the non-European species is unknown.

Native species

Of the 26 species, only three occur in Europe :

Systematics

The World Spider Catalog currently lists 26 species for the genus Meta . (As of June 2020)

In other genera, mainly in the genus of the autumn spider ( Metellina ), the following species were placed between 2016 and 2020:

swell

Individual evidence

  1. ↑ a b Natural History Museum of the Burgergemeinde Bern: World Spider Catalog Version 17.0 - Meta . Retrieved June 14, 2016.

literature

  • Stefan Heimer, Wolfgang Nentwig: Spinnen Mitteleuropas , Blackwell Wissenschafts-Verlag, 1991, ISBN 3-8263-8290-0
  • Heiko Bellmann: The cosmos spider guide. Kosmos-Verlag, Stuttgart 2016. ISBN 978-3-440-15521-9
  • Michael Roberts: The Spiders of Great Britain and Ireland, Vol. 2. Harley Books, 1987. ISBN 978-0-946589-06-7
  • Yuri M. Marusik & Seppo Koponen (1992): A review of Meta (Areneae, Tetragnathidae) with description of two new species. Journal of Arachnology 20: 137-143.
  • Stefano Mammola & Marco Isaia (2014): Niche differentiation in Meta bourneti and M. menardi (Araneae, Tetragnathidae) with notes on the life history. International Journal of Speleology 43 (3): 343-353.
  • Family Tetragnathidae. In: Nentwig W, Blick T, Gloor D, A. Hänggi, C. Kropf: Spinning Europe. www.araneae.unibe.ch, version 11.2016

Web links

Commons : Cave Cycle Web Spiders  - Collection of images, videos and audio files

Meta in the World Spider Catalog