Hood web spiders

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Hood web spiders
Common fat spider (Steatoda bipunctata), female

Common fat spider ( Steatoda bipunctata ), female

Systematics
Class : Arachnids (arachnida)
Order : Spiders (Araneae)
Subordination : Real spiders (Araneomorphae)
Partial order : Entelegynae
Superfamily : Orb web spiders (Araneoidea)
Family : Hood web spiders
Scientific name
Theridiidae
Sundevall , 1833

The hooded web spiders (Theridiidae), also known as ball spiders , are a family of real spiders (Araneomorphae) and belong to the superfamily of orb web spiders (Araneoideae). The family comprises 124 genera and 2472 species . (As of October 2016)

Well-known representatives are the real widows (genus Latrodectus , with representatives in central North America and the European black widow in southern Europe and central Asia to China), who are among the most colorful members of this family. The crested web spiders are common worldwide, but are most common in the temperate zones , subtropics and tropics ; In North America alone, over 300 species of the family in 30 genera are known. More than half of all semi-social spiders belong to this family, which however represents less than 6% of the diversity of all real spiders.

features

Hood-web spiders are small to medium-sized spiders with a round, spherical abdomen and mostly thin, long legs. The back of the body is glossy black, brown to light brown and often more or less colorfully colored with little contrast. A few crested-web spiders have hard bodies with thorns, while others have a considerably elongated abdomen. A special characteristic of the hood-web spiders is a comb made of a series of enlarged, curved and toothed setae on the tarsus of the fourth pair of legs, with which the prey is bound with silk. This comb, which also earned them the name "Comb-footed spider" by Willis John Gertsch , is usually well defined, but can also be greatly reduced.

Many crested web spiders show pronounced sexual dimorphism. In some species, the males are so small that they can hardly be found in their comparatively huge labyrinth networks.

The relatively small eyes sit close together in a group on the front of the prosoma . The eyesight plays a subordinate role for these mainly nocturnal and cave-dwelling animals.

Network construction

Almost all types of families build safety nets. Most crested web spiders are sedentary trappers. But there are also interesting representatives who, like Argyrodes, live as commensals in the nets of other species or Euryopis , who have completely given up netting in favor of a migratory way of life.

Most crested web spiders hang upside down from the underside of their irregularly spun labyrinths of dry threads. They are small spiders that use almost invisible fine threads to build their traps between plants or hide in caves or cracks in the upper soil layer. The nets of the gray-brown house-dwelling Parasteatoda tepidariorum , which quickly become covered with dust and are clearly visible, are much less well hidden .

These seemingly irregular and loose traps are not a random accumulation of irregular and haphazardly spun threads. Rather, they contain some interesting innovations. A crested web spider often weaves a thick sheet of silk as a shelter for the resting spider. Leaves and sand are sometimes used as building materials. The bowl of the boreal Theridion zelotypum appears particularly practical . She ties spruce needles and other parts of plants together to form a stable, waterproof tent under which she hides herself and her eggs like hatched young animals. Other hood-web spiders hang their spherical sacs of ice, not hidden, freely floating between scaffolding threads.

Catching prey

In addition to the central labyrinth, with or without a retreat area, many nets of the canopy web spiders have a series of longer guy lines that attach the entire structure to solid surfaces, for example that of the western black widow ( Latrodectus hesperus ). These guy threads are kept under tension at the lower end by inconspicuous silk threads. If smaller insects run into these ropes, the glue will hold them in place. When their attempts at liberation tear the tension ropes, the elastic and tensioned threads contract and lift the glued insect off the ground.

The crested web spiders approach larger prey, which can sometimes be so large that it has not been lifted or not lifted significantly. At first the spider only turns towards the prey with its hind legs, on whose tarsi it has the combs. She uses it to combed a wide film of sticky silk from her spinning glands, with which she initially only fixes one leg of the prey with a wide, sticky silk ribbon. Only when the prey has been so effectively tied up does the spider approach completely from the front and look for a thin-skinned spot in the chitin shell, usually the joint membranes between the limbs, bite and inject its venom. Only then does she begin the difficult task of moving the still defending insect to a better place in her labyrinth. To do this, she pulls several ropes from her labyrinth net to the prey and the bottom, which are repeatedly pulled up in many small steps until the prey hovers 5 to 7 cm above the ground. Then the meal begins, which in the case of larger insects is large enough to be eaten slowly within three to four days. The sucked out, shrunk package of booty is then released into deeper areas of the labyrinth and thrown on the ground.

Reproduction and brood care

In the outer areas of the net of a female, sexually mature males can be observed at the right time of year, which are not hostile during the mating and courtship season, but are kindly tolerated in the net for a longer period of time and are sometimes even allowed prey there. Occasionally a female kills and eats the male, but contrary to popular belief, this is the exception. The German term "widow" is probably unfounded. The hatched young spend the first few days in the mother's net and are fed with food by her there ( regurgitation feeding ), as in the case of the European Theridion sisyphium and others. a. Crested web spiders have been observed. This is followed by a phase in which young animals are provided with solid food for a few more weeks. To do this, the mother pulls trapped insects into their hiding place with the young animals.

Systematics

The World Spider Catalog currently lists 124 genera and 2472 species for crested web spiders. (As of October 2016)

The genus Theridion

A large percentage of our crested web spiders belong to the genus Theridion ; some of them are bright in color. The spherical female of Theridion differens , 3 millimeters long and with a reddish-brown colored abdomen, which is decorated with a red-yellow stripe at the top, places her large egg sac in her nest. Its web can be found on all kinds of low plants and consists of a small tent that barely covers the spider, from which an irregular network of threads radiates. This tissue also spans several plants. Theridion frondeum is even brighter in color with its pale yellow or whitish basic color and clear black pattern, which can also take on many other colors and shapes. Some representatives of this genus even appear monochrome white without a pattern, others are colored tabby, banded or piebald. These attractive crested web spiders live in the herbaceous and shrub layers and prefer moist, partially shaded places in forests or on streams.

Native genera and species (selection)

Web links

Commons : Crested Web Spiders (Theridiidae)  - Collection of images, videos and audio files

Theridiidae in the World Spider Catalog

literature

Individual evidence

  1. ↑ a b Natural History Museum of the Burgergemeinde Bern: World Spider Catalog Version 17.5 - Theridiidae . Retrieved October 11, 2016.