Dwarf spiders

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Dwarf spiders
Erigone atra - male, a representative of the subfamily

Erigone atra - male, a representative of the subfamily

Systematics
Order : Spiders (Araneae)
Subordination : Real spiders (Araneomorphae)
Partial order : Entelegynae
Superfamily : Orb web spiders (Araneoidea)
Family : Canopy spiders (Linyphiidae)
Subfamily : Dwarf spiders
Scientific name
Erigoninae
Emerton , 1882

The dwarf spiders (Erigoninae Emerton , 1882) are real spiders and belong to the family of canopy spiders (Linyphiidae). Depending on the author, around 400 genera with more than 2,000 species are known. With the exception of New Zealand, they are distributed worldwide, with the main distribution in the moderate (temperate) zones of the Old World. Among other things, these spiders are of central importance in the ecology of agricultural systems . In fact, new research shows that in Central Europe two of the three most active species in insect prey are: Erigone atra (23.5%) and Oedothorax apicatus (14.5%)

description

The spiders are morphologically relatively homogeneous and consistently graceful, with the typical body shape of the Linyphiidae. The male and female mating organs ( pedipalps and epigynes ), which are essential for the diagnosis of species, show large and striking differences . In many, but not all, genera, the males sometimes have long and bizarre shaped protrusions in the head area, the function of which has long been a mystery; in the meantime they have been recognized as carriers of glands that play a role in copulation. Erigoninae are predominantly small spiders 1 to 3 millimeters in length (therefore also called "dwarf spiders"), but some reach 6, in exceptional cases even 10 millimeters in length.

Classically, the European Erigoninae are differentiated from the other Linyphiidae in that they lack a large bristle at the end (distal) of the tibiae of the fourth pair of legs, which is present in the other Linyphiidae (one, opposite two Macrosetae dorsally on the tibia). Another morphological feature is the formation of the trachea in the cephalothorax, in which the central tracheal branches are finely branched (so-called "desmitracheates" trachea system). More recent analyzes including South American and other non-European taxa have shown that these characteristics apply to the European, but not to all Erigoninae.

distribution

Over 300 species are native to Northern Europe, where they make up almost a quarter of the total population of spiders. About 650 species are known in North America. Overall, it can be said that the Erigoninae are mainly found in the boreal regions of the world and less in the southern hemisphere .

Taxonomy

Currently the subfamily is divided into 401 genera according to Tanasevitch and 390 genera according to Platnick :

Genus moved, renamed, no longer in use

Research history

Since the processing of the French arachnologist Eugène Louis Simon in the 1920s, the Linyphiidae family has been divided into two subfamilies, the Erigoninae and the Linyphiinae. Hermann Wiehle even raised the Erigoninae to a family of their own, which he called Micryphantidae. Later revisions on a strictly cladistic basis then showed that the Erigoninae are monophyletic, but the Linyphiinae opposite them represent a paraphyletic parent group. The monophyly of the Erigoninae has been confirmed in recent studies on both a morphological and a molecular basis (by comparing homologous DNA sequences).

Individual evidence

  1. ↑ a b Gustavo Hormiga: Higher Level Phylogenetics of Erigonine Spiders (Araneae, Linyphiidae, Erigoninae). In: Smithsonian Contributions to Zoology. No. 609, 2000.
  2. ^ The role of Perennial habitats for Central European farmland spiders.
  3. ↑ Michael Roberts: The Spiders of Great Britain and Ireland. Vol. 2: Linyphiidae and Check List. Harley Books, Colchester, UK 1987, ISBN 90-04-07667-0 .
  4. ↑ Peter Michalik, Gabriele Uhl: Cephalic Modifications in Dimorphic Dwarf Spiders of the Genus Oedothorax (Erigoninae, Linyphiidae, Araneae) and Their Evolutionary Implications. In: Journal of Morphology. 272, 2011, pp. 814-832. doi: 10.1002 / jmor.10950
  5. ↑ Jeremy A. Miller, Gustavo Hormiga: Clade stability and the addition of data: A case study from erigonine spiders (Araneae: Linyphiidae, Erigoninae). In: Cladistics. 20, 2004, pp. 385-442.
  6. ↑ a b c d e f g h i The world spider catalog, Linyphiidae
  7. ↑ a b c A. V. Tanasevitch: Linyphiid spider of the World.
  8. ↑ Not in the list of genera according to Tanasevitch, but in the list of species
  9. ^ I Nesticidae in the World Spider Catalog
  10. ^ Miquel A. Arnedo, Gustavo Hormiga, Nikolaj Scharff: Higher-level phylogenetics of linyphiid spiders (Araneae, Linyphiidae) based on morphological and molecular evidence. In: Cladistics. 25, 2009, pp. 231-262. doi: 10.1111 / j.1096-0031.2009.00249.x

Web links

Commons : Dwarf Canopy Spiders  - Collection of Images, Videos, and Audio Files

Linyphiidae in the World Spider Catalog