Curling wheel web spinning

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Curling wheel web spinning
Uloborus plumipes

Uloborus plumipes

Systematics
Class : Arachnids (arachnida)
Order : Spiders (Araneae)
Subordination : Real spiders (Araneomorphae)
Partial order : Entelegynae
Superfamily : Uloboroidea
Family : Curling wheel web spinning
Scientific name
Uloboridae
Thorell , 1869

The curling wheel web spiders (Uloboridae) are a family of real spiders from the superfamily of the Uloboroidea . The family currently comprises 18 genera and 281 species . (As of July 2016)

This family of cribellate spiders is widespread in the tropics. Only a few species also advance northward into the temperate zones. Only three species are represented in Central Europe. In Latin America there are two species in the genus Philoponella that live socially in large colonies.

The species have developed amazing camouflage, net building, and trapping methods. Curled wheel web spiders do not have any poison glands and do not produce glue threads. The adhesion of their cribellate trapping wool is based on the structure of tens of thousands of silk fibers with a diameter of only 10 to 15 nanometers , which curl around thicker, more stable framework threads.

Morphology of the native species

The adult animals of the native species Hyptiotes paradoxus , Uloborus plumipes and Uloborus walckenaerius are three to six millimeters long and have a moderately sturdy build. The leg length of an individual is very different, the longest leg (pair of legs I and II) can be twice as long as the body length, the pair of legs III and IV are much shorter. The IV metatarsus is concave. The females have their calamistrum there , which is reduced in the males. Curling wheel web spiders have 3 tarsal claws . You have eight dark eyes in two horizontal lines of four eyes each. The male palpic organs are complex and house the hollow tarsal cymbium . The abdomen ( opisthosoma ) is conspicuously patterned. The females have a plate-shaped cribellum in front of the spinnerets . The cribellum is reduced in the males.

Way of life and network construction

Curled wheel web spiders are camouflage specialists , both in their natural shape and in their way of life. They collect fragments of leaves and other material with which they camouflage themselves, or look deceptively similar to leaves or twigs.

Special and common features of the webs of the crimping wheel web spiders are the web hub, which is tightly and artistically meshed, and the ribbon-shaped ornaments or stabiliments . The original function and origin of the stabilization elements, which some ecribellate orb web spiders (e.g. Argiope , wasp spider ) also incorporate, is unclear. In the Uloboridae it is used to camouflage and increase stability and can facilitate the repair of the damaged network. The most common form of the stabilizing element is a serrated band that runs through the center of the wheel network. It is almost invisible in the area of ​​the hub. But there are numerous variations of this stabilization element, such as a V-shaped course with the hub in the center or crosses, as well as complete or interrupted concentric circles.

The crimping wheel web spider lurks with its belly side facing upward in the hub on the underside of its horizontal web. The legs are stretched forwards and backwards so that the Stabilement connects them to form a complete trap. In the light breeze it is almost indistinguishable from a branch. Females perfect this camouflage method. It aligns its elongated egg packets in a row across the net, which is also completed with remains of prey and other fragments, and stretches itself into the middle between them. This creates a bright line, the individual components of which are difficult to distinguish from one another, while the actual trap is even more difficult to see due to the contrast.

Not all networks are horizontal and not all form a complete wheel. In some species the network is slightly inclined and in others it is more or less vertical. The creation of vertical nets represents a significant ecological difference, as the spider does not have to wait for insects to run or fall, but rather pushes into the airspace of the flying insects . This changes the entire spectrum of food and therefore the entire way of life. The uloborids were therefore often seen earlier as an evolutionary link between the spiders living on the ground and the trappers on high.

The species native to Central Europe build their traps in the crown and shrub layer, in which they hold a gathered signal thread upside down that is attached to the net . This safety net looks similar to the orb of garden spiders , but lies horizontally (in Uloborus ), is formed from only three sectors (in Hyptiotes ), or consists only of a wide band of cribellate fishing silk , as in tropical stick spiders ( miagrammopes ).

Since crinkle-wheel web spiders have no poison glands and claws with which the prey could be stunned or killed, the crimped-wheel web spider only weaves them in immediately.

Systematics and evolution

The Uloboridae and their closest relatives, the Deinopidae family , have long been regarded as the ancestors of the orb web spiders (Araneoidea), as the horizontally woven orb web of the Deinopidae could have developed into a vertical, free-hanging orb web via the web of the crinkle wheel web spiders. The designs are very similar; the web of the orb web spiders (Araneoidae) corresponds to a complete wheel, whereby two sectors seem to be missing in the sector spiders ( Zygiella ), which reappear in the triangular spiders ( Hyptiotes ; Uloboridae). The stabilization elements also appear in some networks of both superfamilies. The great precision exhibited by both the traps of the orb-web spiders and the traps of the crimped-wheel-web spiders seems surprising enough to assume a unique origin in the evolution of order. It also seemed plausible to the arachnologists that the ability of the ecribellate spiders to provide the trapping silk with other different substances such as glue, could have developed at this point in evolution. The orb web spiders were therefore long considered to be descendants of the crimped web spiders.

Today, on the basis of in-depth studies, it is assumed that these complete or partial orb nets of the very large superfamily of orb-web spiders and those of the crinkle-wheel-web spiders are based on very similar principles, but have developed independently of one another. It is probably an analogy . This applies to the design of the traps (stabilizers, wheel nets, sector nets), but also to the formation of the glue threads. It has also taken place independently of one another several times in evolution ( see: cribellate problem ). What ecological circumstance it is thanks to that the curling wheel web spiders can do without poison glands remains unexplained at first.

External system

 (Entelegynae)  
  NN  

 (Development towards "modern spiders")


  NN  

 Orb web spiders (Araneoidea)


  Uloboroidea  

 Ruffled web spiders (Uloboridae)


   

 Deinopidae





  NN  

 Oecobiidae


   

 Hersiliidae


   

 Malkaridae


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Native species

In Central Europe only one species of the genus Hyptiotes and two species of the genus Uloborus have been identified.

Internal system

The World Spider Catalog currently lists 18 genera and 281 species for the curling wheel web spiders. (As of July 2016)

Web links

Commons : Curling-wheel web spiders (Uloboridae)  - Collection of images, videos and audio files

Uloboridae in the World Spider Catalog

literature

  • Gertsch, Willis J. 1979: American Spiders, 2nd edition. Van Nostrand Reinhold, New York, ISBN 0-442-22649-7
  • Theo Blick, Robert Bosmans, Jan Buchar, Peter Gajdoš, Ambros Hänggi, Peter Van Helsdingen, Vlastimil Ružicka, Wojciech Starega & Konrad Thaler: Checklist of the spiders of Central Europe. Checklist of the spiders of Central Europe. (Arachnida: Araneae). Version December 1, 2004. pdf, 1.41 MB

Individual evidence

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