Dark pothead spider

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Dark pothead spider
Dark pachyderm spider (Pachygnatha degeeri), female

Dark Pachygnatha degeeri , female

Systematics
Subordination : Real spiders (Araneomorphae)
Partial order : Entelegynae
Superfamily : Orb web spiders (Araneoidea)
Family : Extensor spiders (Tetragnathidae)
Genre : Thick jaw spiders ( Pachygnatha )
Type : Dark pothead spider
Scientific name
Pachygnatha degeeri
Sundevall , 1830

The dark pothead spider ( Pachygnatha degeeri ) is a spider from the family of the extensor spiders (Tetragnathidae). The species is widespread in the Palearctic and inhabits a large number of habitats, but prefers more humid biotopes and is found there in low vegetation. In its range, it is common in suitable habitats .

Like other thick jaw spiders ( Pachygnatha ), the dark pothead spider is characterized by the hybrid way of life that is typical for the genus. Only young animals in the early stages create an orb web , as is usual for extensor spiders, while in development more advanced young animals and the adult spiders go free-roaming to hunt. In addition, the species is one of those whose young can most often be observed in Central Europe by spreading with the help of the so-called spider flight .

The dark pothead spider may be suitable as an effective control agent in the context of biological pest control against aphids , which are among the preferred prey of the species and can be decimated by them in large quantities. Despite various poisons that are produced by aphids to ward off predators (predators), including the dark pothead spider, the species can eat large numbers of them every day. It is therefore assumed that the spider is resistant to toxins from aphids. This makes the dark pothead spider an interesting research object from a scientific point of view.

features

male

The female of the dark pothead spider reaches a body length of 3.5 to 5 and the male one of 2.5 to 3.5 millimeters. Like all thick jaw spiders ( Pachygnatha ), it is a smaller species of spider. The basic physique is identical to that of other representatives of the genus.

The carapace (back shield of the prosoma or front body) is mostly dark brown in color, but can also be black, especially in the male. The surface of the carapace and, below it, especially that of its edges as well as the cephalic (on the head) area is provided with point-like depressions in places. These depressions strive from the thoracic (on the chest) area in a star shape away from the fovea ( apodem ). The sternum (breast shield of the prosoma) is colored dark brown like the carapace and has depressions similar to the latter area. The chelicerae (jaw claws) are dark brown in color. The legs are yellowish to light brown in color. In addition, they are pale and shiny.

The opisthosoma (abdomen) appears whitish to cream-colored. Dorsally (above) it usually bears a strongly pronounced folium (leaf markings) and median (in the middle) two to three longitudinal silver spots each. These embed the folium and are rather elongated at the front, while they become more rounded and smaller towards the back and sometimes also merge with one another. The flanks of the foil are wavy. Laterally, the opisthosoma is colored white in contrast to its dorsal side. Overall, the staining intensity of the opisthosoma can vary widely.

The sexual dimorphism (difference between the sexes) is not very pronounced, as is the case with all thick jaw spiders. A common distinguishing feature between the two sexes can be the carapace, which is often darker in males. Individual specimens of the dark pothead spider can have greenish-gray or yellow tints, while young animals can have prominent red tones.

  • Dorsal view of a male

  • Frontal view of a male

  • Lateral view of a male

  • Frontal detail of a male with the eyes and chelicerae that are clearly visible here

  • Rear view of a dark pothead spider

Genital morphological features

The globe of the dark pothead spider

A single bulb (male genital organ) of the dark thick jaw spider is within the genus of the thickness jaw spiders ( Pachygnatha characterized) in that the Paracymbium (extension of the Cymbiums, the third sclerite or hard portion of the bulb) is constructed long and pointed, and a lateral tooth with a wide base owns. The epigyne (female sex organ) is characterized within the genus by a slightly curved gap located there. In addition, the vulva is provided with club-shaped spermatheks (seed pockets).

Differentiation from other thick-jawed spiders

The dark pothead spider shares some visual similarities with the genus-related forest pithy spider ( P. listeri ), which is also widespread in Central Europe and , like the dark pothead spider, does not have a tooth-like appendage on the base members of the chelicerae. This distinguishes the two types of the large thickness jaw spider ( P. clercki ), the third is widely used in Central Europe representative of the thickness jaw spiders ( Pachygnatha ), which can be also greater than the other two types. The dark thick jaw spider can be distinguished from the forest thick jaw spider by the mostly darker folium with the more blurred edges, whereby the edges in particular can be colored darker. The prosoma of the dark pothead spider, which appears darker than that of the other two species, can also be used as a distinguishing feature.

Happen

Females found in the village of Audriņi in the Latgale region of Latvia and northwest of Rēzekne .

The distribution area of ​​the dark pothead spider extends from Morocco and Algeria to Europe , Turkey , the Caucasus , Russia (European to Far Eastern part), Iran and Central Asia to China . The species is also extensively represented in Europe itself and has so far only not been detected on the Russian double island of Novaya Zemlya , Iceland and the Balearic Islands, as well as in Asia in Armenia and Cyprus .

In Great Britain, the dark pothead spider is the most common species of the genus and is widespread there with the exception of northern England and northern Scotland , where it is only found scattered. On the island, the kind of heights can be found from under four to over 750 meters above sea level.

Individual finds of the dark pothead spider were also made in South America . However, these are probably due to introductions.

Habitats

The dark pothead spider sometimes lives in meadows , like this one near the village of Wustrow in the Fischland in Mecklenburg-Western Pomerania .

The dark pothead spider is a photophilic (light preferring) and eurytopic ( living in different biotopes ) and open spaces preferring species that inhabits all unforested habitats (habitats). The species' habitats include dry and moist wasteland and clearings as well as meadows and gardens. Ungrazed meadows are the preferred habitat of the dark pothead spider. It also lives in fields and, as a halotolerant (salt-bearing) species , it also lives in salt marshes on the North Sea .

In Great Britain, the dark pothead spider could also be detected in grasslands (here especially in crevices and tussocks ) and quarries , on roadsides and even in debris created by households . Finds of the species were also made in Great Britain on forest roads and dilapidated industrial sites. Still, the dark pothead spider generally prefers more humid microhabitats .

Deviations from the habitats of other thick-jawed spiders

The dark pothead spider, like the large one ( Pachygnatha clercki ) and the forest pithead spider ( Pachygnatha listeri ), is common in Central Europe and is often found in high density in Germany . In the same way, all three species share some habitats. However, the dark pothead spider, in contrast to the large and the forest pothead spider, does not show a strong bondage to moisture. It is also the only one of the three species that can also be found in relatively dry and sunny biotopes. Furthermore, the dark pothead spider remains hidden less deeply in the vegetation than the other two representatives of the genus and can therefore be found more easily.

way of life

Active female during the day

The dark pothead spider can be found in close proximity to the ground or in low vegetation. With other thick- jawed spiders ( Pachygnatha ) it shares the typical hybrid way of life for the genus, so that only young animals, but no longer adult spiders, create spider webs. In 1978, however, it was shown under laboratory conditions that at least adult females of the dark pothead spider like to create dense and widely branched webs within these conditions, in which they occasionally stay, but were not bound to them. The animals in these webs were able to move without any problems.

Hunting behavior and range of prey

The hunting method of the dark pothead spider also corresponds to that of other species of the genus. Young animals under a size of two millimeters create an orb web like other extensor spiders (Tetragnathidae) for the purpose of catching prey . These are of small diameter, laid out horizontally and are attached to the stems of various plants near the ground.

In contrast, more advanced young animals with a body length of over two millimeters and adult spiders hunt freely by searching the ground. Their hunting style thus corresponds to that of the running spiders ( Philodromidae) and the hunting spiders (Pisauridae). The change in hunting strategy of dark thick pine spider in advancing age can thus establish that the spinnerets located and necessary for the construction of cobwebs silk glands , aggregatae called glands and the glands flagelliformes, regress with advancing age and in adult spiders do are no longer present, while they are still well developed in the young animals.

The prey spectrum of the dark pothead spider is made up of smaller insects , including aphids and springtails in particular .

Life cycle and phenology

The life cycle of the dark thick jaw spider basically also corresponds to that of other thick jaw spiders ( Pachygnatha ). The phenology (activity time) of the species amounts to the whole year in adult individuals of both sexes. In Central Europe, the peak activity period is between April and June. This is also the case in the UK in the summer.

The pairing takes about two hours. In this case, the male grasps the basal segments of the female with the help of his chelicerae and thus keeps them closed. The female grasped from above is thus prevented from capturing the male. A similar mating behavior occurs in the forest pothole spider ( P. listeri ), while in the large pothole spider ( P. clercki ) the male holds the chelicerae of the female, which has been spread out, between the basal segments and the trapping furrows of his own chelicerae. This ability is given to this species by the tooth-like process present on the basal segments of the chelicerae of the male, which the other two species lack.

Some time after mating, the female makes a flat and whitish to yellowish colored egg cocoon , which it hides in the litter layer , under stones or in layers of moss . The hatched young animals then spread via the so-called spider flight . The dark pothead spider is generally one of the species that can be observed more frequently.

Systematics

Classical systematics in the field of biology deals with the taxonomic (systematic) classification as well as with the biology and with the nomenclature (discipline of scientific naming) of living beings and thus also those of the dark pothead spider.

With the species name degeeri want Swedish entomologist Charles De Geer be honored.

Description history and synonymy

The Dark Dick pine spider was already in their 1830 took place and Carl Jakob Sundevall performed first description , the term Pachygnatha degeerii , which thus largely corresponds valid today. In the past, the species was not infrequently described as a web-building spider, until the typical way of life of the thick- jawed spider ( Pachygnatha ) together with the dark- colored thick- jawed spider was analyzed in more detail in 1978.

The 1985 by Jin-Lin Hu and Wen-Gui Wu first-described type Dyschiriognatha yiliensis was in 1999 with the dark thick pine spider synonymised because the characteristics of the region Xinjiang derived types (for the first description used copies) of yiliensis D. with those of dark thick pine spider to match.

Subspecies

In addition to the nominate form P. d. degeeri there is the subspecies P. d. dysdericolor of the dark pothead spider, which was first described by Rudy Jocqué in 1977 . For this he used a male that he found under a bridge about a kilometer northeast of the dam in the town of Lalla Takerkoust near the Moroccan city ​​of Marrakech .

The subspecies does not differ significantly from the nominate form. Essential features are the uniformly light red coloring of the carapace and all extremities including the pedipalps as well as the uniformly white colored opisthosoma. Due to its coloring, the subspecies is reminiscent of a spider from the genus woodlouse ( Dysdera ) within the family of six- eyed spiders (Dysderidae), which is where the name dysdericolor comes from.

External system

By phylogenetic (the lineage in question) studies of the British Isles occurring species of spider it was possible the familial relationship of dark thick pine spider who also found there the Great ( P. clercki ) and the forest thick pine spider ( P. listeri to explore). The present and 2018 identified information of the three kinds of the thickness jaw spiders ( Pachygnatha ) are based on their morphological (whose structure and shape concerned) properties, which moreover using DNA barcoding determined nucleotide sequences of the species to be supported. Among the other two species, the forest pothead spider is the most closely related species to the dark pothead spider and is therefore its sister species . The following cladogram illustrates the external systematics of the three types of each other:

  Thick jaw spiders ( Pachygnatha ) 

 Big jaw spider ( P. clercki )


   

 Dark pothead spider


   

 Forest spider ( P. listeri )




Dark pothead spider and human

The dark pothead spider has different relationships with humans. The species is believed to be useful in the context of biological pest control against aphids .

The dark pothead spider as a suspected beneficial insect

The possibility of ascribing an agricultural benefit to the dark pothead spider through its preference for aphids as prey has been increasingly explored in the United Kingdom . In studies that have already been carried out in the local agro-ecosystem in 1992, 1993, 1994 and 2005, the species could only be detected in these locations in a small number of individuals. Winter wheat crops in the British Isles tend to be dominated by canopy spiders (Linyphiidae), while in contrast elsewhere in Europe the dark pothead spider can be present in agricultural crops in higher population densities. Therefore, the species there can be one of the most important predators (predators) of aphids and possibly other pests . Although the dark pothead spider is seldom found in British cereal crops compared to the canopy spiders, the species there occupies an important position in the diverse set of predators and a different niche than the newly built canopy spiders.

In contrast to the female individuals of the canopy spiders, who are tied to their nets and therefore very loyal to their location, both sexes of the dark pothead spider ( Pachygnatha ) are active hunters and therefore have an identical range of prey , which may also be less pronounced here Sex dimorphism explained. The investigations revealed a significantly larger amount of remains of aphids in the intestines of individuals of the dark pothead spider than in canopy spiders found at the same locations. Accordingly, aphids make up a considerable proportion of prey animals of the species. The representatives of the thick jaw spider including the dark thick jaw spider prevent aphids fallen from plants from climbing them again and prey the aphids by night climbing on the plants selectively in the area of ​​the umbrella . The spiders within this ecological niche consume a large number of aphids. It is not clear why aphids make up a large part of the prey of the dark pothead spider. Presumably, the lice form a more optimal prey for the spider than for other predators of it.

It is assumed that the dark pothead spider, like various ladybirds , in which aphids make up a large part of the prey animals, has developed a certain resistance to aphid poisons and can therefore easily consume larger quantities of aphids than other spiders. Likewise, the comparatively large proportion of aphids consumed by the spider can also be attributed to the fact that at the time of the investigations there were no other possible prey at the locations there and the individuals of the dark pothead spider would be forced to eat the aphids, regardless of whether whether this could have led to a decrease in the fitness of the individuals of the dark pothole spider. Particularly in the base area in turn seem springtails from the families of Isotomidae which Entomobryidae and Sminthuridae to form the main prey of dark thick pine spider. However, it is unlikely that free-roaming spiders such as the dark pothead spider consume large quantities of these prey, as catching the very active springtails is likely to be a laborious process for these spiders. In contrast, the springtails are their preferred prey for the smaller canopy spiders that occur on the ground and whose nets make it easier to catch the springtails. Larger and less agile prey animals, which would be more suitable for the dark pothead spider, rarely appear in these areas.

Although only 6% of all spiders found in the investigated areas belonged to the dark pothead spider in the research, the total amount of remaining components in the intestines of the populations of this species was considerably high compared to other spider species. Although the existing populations of canopy spiders were generally larger and captured a larger number of aphids, individual individuals of the dark pothead spider still captured more aphids than those of the canopy spiders and can therefore prove to be a more effective way of controlling aphids. Between May and July of this year, males of the dark pothead spider in particular captured hardly any lower numbers of aphids than the canopy spiders there, although the number of the latter was significantly higher there. As with the canopy spiders, specimens of the dark pothead spider also fed disproportionately more often on aphids if these were relatively rare during their establishment phase, which turns the spiders into opportunistic predators, which can nevertheless effectively reduce the population density of aphids. In July 1999, however, the hunting activity of the investigated individuals of the dark pothead spider for aphids no longer increased, which was possibly the result of the food requirements met by the previous hunting successes.

Various spiders of other species, which were identified during the research in the areas investigated and which occurred even more rarely than the dark pothead spider, fed on aphids significantly less often. The use of specific and monoclonal antibodies of the aphids themselves proved that the dark pothead spider feeds on aphids to a not inconsiderable extent and is therefore suitable as a suitable agent in the context of biological pest control.

Danger

The threats to the existence of the dark pothead spider are assessed differently depending on the country and region. In the Red List of Threatened Species of Animals, Plants and Fungi in Germany and the Red List and Total Species List of Spiders in Germany (2016), the species is rated as "not endangered " because the species is very common in Germany and its populations there are long-term as well as being constant in the short term. There was also no change to the previous Red List from 1996. In the Red List of Spiders in Carinthia (1999), the populations of the dark thick-jawed spider are also rated equally.

In the Red List of Great Britain (1991) the dark pothead spider, which is also common there, is recorded according to IUCN standards in the category LC (“Least Concern”, or not endangered). The same applies to the Red List of Arachnida (Arachnida) Norway (2015), while the endangerment level of the species is rated in the Red List of Spiders in the Czech Republic in the category ES (“Ecologically Sustainable” or ecologically adaptable).

Individual evidence

  1. ↑ a b c d e f g h i j k Pachygnatha degeeri at the Wiki der Arachnologische Gesellschaft e. V., accessed on July 14, 2021.
  2. ↑ a b c d e f g h i Pachygnatha degeeri at araneae - Spiders of Europe, accessed on July 13, 2021.
  3. ↑ a b c d e f g h i j k l m Nicolaj Klapkarek: Dark thick jaw spider - Pachygnatha degeeri SUNDEVALL, 1830. In: Nature in NRW. State Office for Nature, Environment and Consumer Protection North Rhine-Westphalia, accessed on July 15, 2021 .
  4. ↑ a b Lawrence Bee, Geoff Oxford, Helen Smith: Britain's Spiders: A Field Guide - Fully Revised and Updated Second Edition (=  WILDGuides of Britain & Europe ). Princeton University Press, 2020, ISBN 978-0-691-21180-0 , pp. 118 .
  5. ^ Michael John Roberts: The Spiders of Great Britain and Ireland (=  The Spiders of Great Britain and Ireland . Volume 2 ). Brill Archive, 1985, ISBN 978-90-04-07658-7 , pp. 199 .
  6. ↑ a b c d e f Heiko Bellmann: The cosmos spider guide . Kosmos, 2016, ISBN 978-3-440-15521-9 , pp. 122 .
  7. ↑ a b c d e Pachygnatha degeeri at the British Arachnological Society, accessed June 15, 2021.
  8. ↑ a b c Pachygnatha at the Wiki der Arachnologische Gesellschaft e. V., accessed on July 15, 2021.
  9. ↑ a b Dieter Martin: On the construction of the cycle network of the genus Pachygnatha Sund. (Araneae: Tetragnathidae) . In: Zoosystematics and Evolution . tape 54 , no. 1 . Academy of Agricultural Sciences of the GDR , Berlin 1978, p. 84 , doi : 10.1002 / mmnz.19780540104 ( pdfslide.tips [accessed July 15, 2021]).
  10. ↑ Dieter Martin: To the construction of the cycle network of the genus Pachygnatha Sund. (Araneae: Tetragnathidae) . In: Zoosystematics and Evolution . tape 54 , no. 1 . Academy of Agricultural Sciences of the GDR , Berlin 1978, p. 84–85 , doi : 10.1002 / mmnz.19780540104 ( pdfslide.tips [accessed July 17, 2021]).
  11. ↑ Dieter Martin: To the construction of the cycle network of the genus Pachygnatha Sund. (Araneae: Tetragnathidae) . In: Zoosystematics and Evolution . tape 54 , no. 1 . Academy of Agricultural Sciences of the GDR , Berlin 1978, p. 93 , doi : 10.1002 / mmnz.19780540104 ( pdfslide.tips [accessed July 15, 2021]).
  12. ↑ a b c Charles D. Dondale, James H. Speaker: The Orb-Weaving Spiders of Canada and Alaska, Araneae: Uloboridae, Tetragnathidae, Araneidae, Theridiosomatidae . In: Research Branch Agriculture Canada Publication . Canadian Science Publishing, Ottawa 2003, ISBN 0-660-18898-8 , pp. 88 .
  13. ↑ William Eberhard, Bernhard A. Huber: Courtship, copulation, and sperm transfer in Leucauge mariana (Araneae, Tetragnahidae) with implications for higher classification . In: Journal of Arachnology . tape 26 , no. 3 . American Museum of Natural History , January 1998, p. 365 ( researchgate.net [PDF; accessed July 15, 2021]).
  14. ↑ Natural History Museum of the Burgergemeinde Bern: World Spider Catalog - Pachygnatha degeeri . Retrieved July 16, 2021.
  15. ↑ Jin-Lin Hu, Wen-Gui Wu: Notes on Xinjiang Uygur Autonomous Region, China [.] Tow [sic] species of spiders of the family Tetragnathidae (Araneida) . In: Journal of Shadong University, Natural Sciences . tape 20 , no. 1 . Chinese Academy of Sciences , 1985, p. 96 .
  16. ↑ a b Rudy Jocqué: Sur une collection estivale d'araignées du Maroc . In: Bulletin & Annales de la Société Entomologique de Belgique . tape 113 , no. 1 , 1977, p. 333 .
  17. ^ Rainer Breitling: A completely resolved phylogenetic tree of British spiders . In: Zoology . University of Manchester , Manchester 14 March 2021, p. 15 , doi : 10.1101 / 2021.03.12.434792 ( biorxiv.org [PDF; accessed on July 17, 2021]).
  18. ^ Rainer Breitling: A completely resolved phylogenetic tree of British spiders . In: Zoology . Manchester University Press , Manchester 14 March 2021, pp. Legend , doi : 10.1101 / 2021.03.12.434792 ( biorxiv.org [PDF; accessed on July 17, 2021]).
  19. ↑ James Harwood, Keith Sunderland, William OC Symondson: Monoclonal antibodies reveal the potential of the tetragnathid spider Pachygnatha degeeri (Araneae: Tetragnathidae) as an aphid predator . In: Bulletin of Entomological Research . tape 95 , no. 2 . University Press of Kentucky , Lexington May 2005, pp. 165 , doi : 10.1079 / BER2004346 ( uky.edu [PDF; accessed on July 14, 2021]).
  20. ↑ James Harwood, Keith Sunderland, William OC Symondson: Monoclonal antibodies reveal the potential of the tetragnathid spider Pachygnatha degeeri (Araneae: Tetragnathidae) as an aphid predator . In: Bulletin of Entomological Research . tape 95 , no. 2 . University Press of Kentucky , Lexington May 2005, pp. 165–166 , doi : 10.1079 / BER2004346 ( uky.edu [PDF; accessed July 15, 2021]).
  21. ↑ a b c James Harwood, Keith Sunderland, William OC Symondson: Monoclonal antibodies reveal the potential of the tetragnathid spider Pachygnatha degeeri (Araneae: Tetragnathidae) as an aphid predator . In: Bulletin of Entomological Research . tape 95 , no. 2 . University Press of Kentucky , Lexington May 2005, pp. 166 , doi : 10.1079 / BER2004346 ( uky.edu [PDF; accessed on July 15, 2021]).
  22. ↑ Pachygnatha degeeri at the Red List Center, accessed on July 16, 2021.

literature

  • Heiko Bellmann: The cosmos spider guide . Kosmos, 2016, ISBN 978-3-440-15521-9 (432 pages).
  • Lawrence Bee, Geoff Oxford, Helen Smith: Britain's Spiders: A Field Guide - Fully Revised and Updated Second Edition (=  WILDGuides of Britain & Europe ). Princeton University Press, 2020, ISBN 978-0-691-21180-0 (496 pages).
  • Michael John Roberts: The Spiders of Great Britain and Ireland (=  The Spiders of Great Britain and Ireland . Volume 2 ). Brill Archive, 1985, ISBN 978-90-04-07658-7 (256 pages).
  • Dieter Martin: To the construction of the cycle network of the genus Pachygnatha Sund. (Araneae: Tetragnathidae) . In: Zoosystematics and Evolution . tape 54 , no. 1 . Academy of Agricultural Sciences of the GDR , Berlin 1971, p. 83–95 , doi : 10.1002 / mmnz.19780540104 ( pdfslide.tips [accessed July 15, 2021]).
  • Jin-Lin Hu, Wen-Gui Wu: Notes on Xinjiang Uygur Autonomous Region, China [.] Tow [sic] species of spiders of the family Tetragnathidae (Araneida) . In: Journal of Shadong University, Natural Sciences . tape 20 , no. 1 . Chinese Academy of Sciences , 1985, p. 95-104 .
  • Rudy Jocqué: Sur une collection estivale d'araignées du Maroc . In: Bulletin & Annales de la Société Entomologique de Belgique . tape 113 , no. 1 , 1977, p. 321-337 .
  • James Harwood, Keith Sunderland, William OC Symondson: Monoclonal antibodies reveal the potential of the tetragnathid spider Pachygnatha degeeri (Araneae: Tetragnathidae) as an aphid predator . In: Bulletin of Entomological Research . tape 95 , no. 2 . University Press of Kentucky , Lexington May 2005, pp. 161–167 , doi : 10.1079 / BER2004346 ( uky.edu [PDF; accessed July 14, 2021]).

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