Triangle Fat Spider

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Triangle Fat Spider
Triangular fat spider (Steatoda triangulosa), female

Triangle fat spider ( Steatoda triangulosa ), female

systematics
Subordination : True web spiders (Araneomorphae)
partial order : Entelegynae
Superfamily : Orb-web spiders (Araneoidea)
family : Crested Web Spiders (Theridiidae)
genus : Fat spiders ( Steatoda )
Type : Triangle Fat Spider
Scientific name
Steatoda triangulosa
( Walckenaer , 1802)

The triangular fat spider or heat-loving orb spider ( Steatoda triangulosa ) is a spider in the crested web spider family ( Theridiidae ). The species is also known as the brown widow , but should not be confused with the brown widow ( L. geometricus ) of the same name, which belongs to the true widow genus ( Latrodectus ) within the same family. The triangular fat spider, originally only distributed in the Palaearctic , was found in America and on the island of St. Helena and on theCanary Islands and seems to be spreading in Europe at the moment.

features

male

The female of the triangle fat spider reaches a body length of 3.5 to 8.6 and the male of 3.5 to 5 millimeters. The basic physique of the species corresponds to that of other fat spiders ( Steatoda ).

The prosoma (front body) appears wrinkled overall and is 1.8 to 2 millimeters long in females and 1.6 to 2 millimeters in males. It is red to black-brown in color and also very shiny. The prosoma has no patterns. The chelicerae (jaw claws), which are also shiny , are brown in colour.

The legs are pale brown in the female and orange in the male. The femora (thighs) and tibiae (splints) are faintly darkly ringed. The legs may also be darkened distally (away from the center of the body).

The opisthosoma (abdomen) is strongly arched. Its coloring ranges from reddish to almost black. Most often it is colored dark brown. In contrast to the prosoma, the opisthosoma is strikingly patterned. The markings are composed of lateral (lateral) bands and a median (middle) longitudinal row of diamond-shaped spots. Fine, net-like and dark lines run through all the drawing elements. These stand in stark contrast to the otherwise rather inconspicuous coloring of the spider and thus give it a characteristic appearance. However, since the expression of the character elements varies greatly, individuals of the triangle fat spider can appear both very light and very dark.

  • Detail views of a female

  • Frontal detail view of a female with clearly visible eyes, chelicerae and pedipalps .

  • Dorsal detail of the carapace of a female

  • Dorsal detail view of the opisthosoma of a female

  • Ventral detail view of the opisthosoma of a female with easily recognizable spinnerets

Genital morphological features

The conductor (head) of a single bulb (male sex organ) is long compared to that of other steatoda spiders and is also curved. In addition, in the male, the tibia of each pedipalp (converted extremity in the head area) is longer than the cymbium (frontmost sclerite or hard part of the globe). The epigyne (female sex organ) is characterized within the genus by its small and rounded appearance.

Differentiation from other fat spiders

It is possible to confuse the triangular fat spider with some other species of fat spider ( Steatoda ) found in Europe , such as the similarly sized common fat spider ( S. bipunctata ). In this case, however, the opisthosoma is less curved, especially since the diamond pattern found in the triangular fat spider is missing. With a body length of 10 millimeters in the female, the large fat spider ( S. grossa ) can be distinguished from the triangular fat spider by its longer legs, above all apart from the different markings on the opisthosoma here. The false black widow ( S. paykulliana ) reaches a much higher body length as a female with 13 millimeters and otherwise differs from the triangular fat spider by the dark brown to black coloration together with the clearly different character elements on the opisthosoma.

In North America , the triangle fat spider can also be confused with the species S. borealis that occurs there, which also remotely resembles the triangle fat spider. However, the opisthosoma of this species is darker in color and has a narrow, light-colored median band.

Happen

Size comparison of a female found in a garage in the Dutch town of Kampen in 2005 .

The triangle fat spider has a large distribution area, which extends from Europe to Turkey , Caucasus , Russia (Europe to the Far East ), Kazakhstan and Iran to Central Asia , among other places . The species has also been introduced to Canada , the United States and the Canary Islands . In addition, occurrences of the species from the island of St. Helena and South America are known.

In Europe itself, the triangle fat spider is also widespread and has so far only been found in continental Europe in Finland , Sweden , Norway , Estonia , the western European part of Russia, Lithuania , Kaliningrad Oblast , Belarus and the Republic of Moldova and elsewhere on the Franz-Josef archipelago -Land and Spitsbergen of the Russian double island Novaya Zemlya , Iceland and the island of Ireland not detected. In the Caucasus, evidence of the spider from Armenia is lacking . In Europe, the triangle fat spider shows tendencies to spread. However, it is not considered an invasive species, since the spider is native to Europe anyway.

The populations of the triangle fat spider in Great Britain are probably also due to introductions. Here the species is mainly found in areas of southern England that are heavily populated by humans .

habitats

Female in a building found in the municipality of Segonzano in northern Italy .

The triangle fat spider is thermophilic (preferring high temperatures) and adopts primarily caves , dunes , forests , garigue , fallow land , swamps , rocky seashores and generally salty coastal areas as habitats . In southern Europe , the species can also be found in dry, sunny places under stones.

In Central Europe , where surviving in the wild is made more difficult by the local climatic conditions, the triangular fat spider is mainly found in buildings. Since the spread of the species in Europe, including Central Europe, individual individuals of the spider can also be found on house walls in Central Europe in summer. In North America, the triangular fat spider shows similar preferences as in Central Europe and consequently lives there synanthropically (preferring human settlement areas) in and on buildings.

frequency and hazard

Female found in 2007 in the Nied district of Frankfurt am Main .

The abundance of the triangle fat spider varies by geographic location due to its preference for the habitats it adopts. The species is therefore more common in southern Europe, while it has so far been rather rare in central Europe. In Germany , however, the spider is more common in warmer areas, including the Main area and the Upper Rhine area. To the north, the triangle fat spider becomes much rarer. Nevertheless, the species is probably spreading in Germany as a result of global warming and is becoming increasingly common in the country. The spider has been established in Germany since 1937 at the earliest. In North America, the triangle fat spider is now also frequently found in human settlements, while it is rarely found in South America.

The threat to the existence of the triangular fat spider is also assessed differently depending on the country and region. In the red list of endangered animals, plants and fungi in Germany or the red list and total species list of spiders in Germany (2016), the stocks of the species are not assessed. In the previous version of the Red List, the species was still considered endangered. However, the reasons for the change of category in the subsequent Red List cannot be determined.

In the Red List of Great Britain (1991), the triangular fat spider is classified as in Germany according to the IUCN standard in the category NA (“Not Applicable” or not assessable). The same is with the Red List of arachnids (Arachnida) Norway's the case, while the way in the Red List of the Spiders (2015) Czech Republic is detected (2015) in the category in the category ES ( "Ecologically Sustainable" or ecologically adaptable) .

way of life

Like all crested web spiders (Theridiidae), the triangle fat spider is nocturnal and creates a crested web that is common for the family and gives it its name . This is used by the predatory species, like all spiders , to acquire prey.

Hunting behavior and range of prey

female in his fishing net

Like all spiders that use a spider web to catch prey , the triangle fat spider is an ambush hunter . The web of the species is particularly popular with individuals of this species in and on buildings in corners of rooms, under ceiling areas and in niches of windows, while in the open air the undersides of stones are popular web building sites for the spider. In terms of the basic type, it corresponds to the irregularly laid out hood web typical of hooded web spiders (Theridiidae). The construct is very similar to the net of the common fat spider ( S. bipunctata ), which belongs to the same genus , but is especially designed for catching ground-dwelling insects .

females with prey
Beetle angle spider
Huissteatodaplusprooic.jpg Angle spider Ball spider Steatoda triangulosa01.jpg

The way of hunting also corresponds to that of other members of this family. The triangular fat spider waits in its web for any prey. If one gets caught in the web, the spider goes to the prey and wraps it in spider silk from a safe distance . The comb-like formations of serrated bristles on the fourth pair of legs, which are usual for crested web spiders, are also used in the triangular fat spider, which serve to form sticky silk for weaving in prey objects. If the prey is sufficiently immobilized, the spider goes straight to it and gives it a venomous bite , which prevents it from escaping and fighting back.

The triangle fat spider is basically an opportunistic hunter with no specialized food spectrum. According to the net designed for catching ground-dwelling arthropods , such species in particular are increasingly being caught. Common prey items include mosquitoes , younger isopods, and brush-footed insects, as well as other spiders. Comparatively large and strong representatives of the latter group, such as angle spiders or trapdoor spiders , are also preyed on by the triangle fat spider. Ants are particularly common, however .

Life cycle and phenology

The life cycle corresponds in principle to that of other fat spiders ( Steatoda ). The phenology (period of activity) of adult individuals is between April and December for females and somewhat shorter between May and December for males.

The pairing seems from early spring to late autumn to take place in the triangle-fat spider. Females of the species with egg cocoons can also be found during the same period . A female can produce several cocoons, which are then often deposited close together in niches and corners in buildings. A single cocoon is teardrop-shaped and about the same size as its maker. It contains about 30 eggs that shine through the loose webbing of the cocoon.

  • Males and females together in the female's web

  • Females with egg sacs

  • Several hatchlings and egg sacs in the mother's web

  • Juvenile specimen

systematics

The system of the triangular fat spider has undergone several changes. The species name triangulosa is a modification of the Latin adjective triangulos , which translated means "triangular". He points to the yellowish markings appearing in triangles on the spider's opisthosoma. The German-language trivial name of the species also comes from this property.

description history

The triangular fat spider was considered to belong to the genus Aranea during its first description in 1802 by the author Charles Athanase Walckenaer, like all spider species at the time , and was given the designation A. triangulosa . The species was first transferred to the genus of fat spiders ( Steatoda ) under the designation S. venustissima in 1850 by Carl Ludwig Koch . The name S. triangulosa , which is common today , was first used in 1873 by Tamerlan Thorell . Since Joon Namkung's use of the term in 1964, this term has been used consistently for the triangle fat spider.

Synonymized species

3 former species were synonymous with the triangular fat spider and thus lost their species status. These types were:

  • Steatoda flavomaculata ( Lucas , 1846) – Synonymized with the triangle fat spider under Levy & Amitai, 1982.
  • Steatoda lugubris ( Thighs , 1963) – Synonymized with the triangle fat spider under Zhu, 1998.
  • Steatoda saylori ( Fox , 1940) – Synonymized with the triangle fat spider under Levi, 1957.

subspecies

In addition to the nonimate form S. t. triangulosa there is also the subspecies S. t. concolor of the triangle fat spider, which was first described in 1933 by Lodovico di Caporiacco . However, this subspecies is considered a Species inquirenda (Phantomart), so its status is in doubt.

The triangle fat spider as a possible beneficial

A benefit in the context of biological pest control is seen in the triangular fat spider , since the prey spectrum of the species also includes pests such as ticks or possibly woodlice (Armadillidiidae). In addition, the spider is said to be an important predator (predator) of the red fire ant (Solenopsis invicta), which can damage electrical equipment if infested. The spider species Loxosceles reclusa , which is potentially dangerous for humans , can possibly be kept away from buildings by the triangular fat spider, as it is also a common prey of the triangular fat spider.

itemizations

  1. ^ a b c d e f g h i Wolfgang Nentwig, Robert Bosmans, Daniel Gloor, Ambros Hänggi, Christian Kropf: Steatoda triangulosa (Walckenaer, 1802). In: araneae - Spiders of Europe. Natural History Museum Bern , retrieved December 3, 2021 .
  2. ↑ a b c d e f g h i j k Svenja Christian: Steatoda triangulosa (WALCKENAER, 1802). (HTML) In: Nature in NRW. State Office for Nature, Environment and Consumer Protection of North Rhine-Westphalia , retrieved December 3, 2021 .
  3. ↑ a b c d Heiko Bellmann: The Cosmos Spider Guide . Cosmos, 2016, ISBN 978-3-440-15521-9 , pp. 88 .
  4. ↑ a b c d e f g h Triangulate cobweb spider. (html) In: Arthropod Museum. University of Arkansas , accessed December 4, 2021 (English).
  5. ↑ a b c Summary for Steatoda triangulosa (Araneae). (PHP) In: Spider Recording Scheme. British Arachnological Society, accessed 4 December 2021 (English).
  6. ↑ a b detail page. (HTPPS) Red List Center accessed 3 December 2021 .
  7. ↑ Steatoda triangulosa. (HTPPS) In: Spider Forum Wiki. Arachnological Society , retrieved December 3, 2021 .
  8. ↑ Charles Athanase Walckenaer: Faune parisienne. insects ou Histoire abrégée des insectes de environs de Paris . Paris 1802, p. 207 .
  9. ↑ Natural History Museum of the Burgergemeinde Bern: World Spider Catalog - Steatoda triangulosa . Retrieved December 4, 2021.
  10. ↑ Natural History Museum of the Burgergemeinde Bern: World Spider Catalog - Steatoda . Retrieved December 4, 2021.
  11. ↑ Wolfgang Nentwig, Robert Bosmans, Daniel Gloor, Ambros Hänggi, Christian Kropf: Steatoda triangulosa concolor (Caporiacco, 1933). In: araneae - Spiders of Europe. Natural History Museum Bern , retrieved December 4, 2021 .
  12. ↑ Hank Guarisco: Predation of Two Common House Spiders upon Medically Significant Pests . In: Transactions of the Kansas Academy of Science . tape 94 , no. 1-2 , 1991, pp. 80 .

literature

  • Heiko Bellmann: The Cosmos Spider Guide . Cosmos, 2016, ISBN 978-3-440-15521-9 (432 pp.).
  • Hank Guarisco: Predation of Two Common House Spiders upon Medically Significant Pests . In: Transactions of the Kansas Academy of Science . tape 94 , no. 1-2 , 1991, pp. 79-81 .
  • Charles Athanase Walckenaer: Faune parisienne. insects ou Histoire abrégée des insectes de environs de Paris . Paris 1802, p. 187-250 .

web links

Commons : Triangle Fat Spider  - Collection of images, videos and audio files