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Atypus affinis

By Lama Bandar

Geographic Range

Purse-web spiders are distributed throughout southern England and can also be found throughout the British Isles. They are also common on the Iberian peninsula and can be found as far north as Denmark and Sweeden and as far south as Northern Africa. ("Summary for Atypus affinis", 2010; Pedersen and Loeschcke, 2001)

Habitat

Purse-web spiders are found in a variety of different European habitats. Most individuals are found in dry, sparse woodlands, calcareous grasslands and heathlands, but the species is also found in sand dunes and rocks, screes, cliff, or quarry habitats. This species most commonly uses areas with sparse, vegetative ground cover. They dig vertical burrows that can be up to 90 cm deep, depending on soil conditions. ("Purse-web spider (atypus affinis)", 2003; "Summary for Atypus affinis", 2010; Pedersen and Loeschcke, 2001; Rezac, et al., 2006)

Physical Description

Purse-web spiders are mygalomorphs (fangs point straight downward vs. crossing each other) with two pairs of book lungs and posterior spinnerets with three segments. This spinneret morphology distinguishes it from the closely related Atypus muralis, whose spinners have four segments. Their bodies are light olive-green in color with brown, oval shaped scutums. Purse-web spiders have eight legs and two main body segments, the cephalothorax and abdomen. Their legs are stocky and they have stout chelicerae projecting from square carapaces. The base of each chelicera contains a venom gland with a duct leading to the tip of the fang. Males average 7-9 mm in length and have thinner abdomens and longer legs than females, which tend to be larger, averaging 10-15 mm in length. ("Purse-web spider (atypus affinis)", 2003; Newton, 2004; Pedersen and Loeschcke, 2001; Roberts, 1985)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    7 to 15 mm
    0.28 to 0.59 in

Development

Purse-web spiders undergo the same simple three stage metamorphosis of all spiders: embryonic, larval, and nympho-imaginal, with each stage separated by a molt. Eggs are fertilized in the uterus externus. Sperm moves towards the center of the egg, as does the female pronucleus, and conjugation of the two nuclei occurs 1-2 hours later. The zygote undergoes cleavage, forming a thin blastoderm with a concentrated yolk center (blastula) after 35 hours. The perivitelline, fluid-filled blastocoel is created by the sinking of the yolk granules. The polarity of the embryo emerges after the blastula contracts. The embryonic and larval stages do not possess developed organ systems and the larval stage is unable to feed independently, relying on yolk for nutrition. Once spiders reach the nympho-imaginal period, they are self-sufficient. The nymph (juvenile) and imago (adult) are very similar, differing only in sexual maturity. (Folex, 2011; Newton, 2004)

Reproduction

During mating season (autumn, typically), males locate females' burrows and tap the outer silk tube of her web. If the female is receptive, he will be allowed to enter the burrow and they will mate for several hours. Breeding partners will live together in the female's burrow until the death of the male; the female then consumes the male's body which provides nutrients for the developing eggs. ("Atypus Affinis Purse-web Spider", 2010; Pedersen and Loeschcke, 2001)

Female and male purse-web spiders generally do not reach sexual maturity until 3 years of age; average age at sexual maturity is 4 years. After copulation, females produce an egg cocoon the following summer which is suspended in the tube of her web. Juveniles remain in the burrow until after their second instar (approximately 18 months after initial copulation). No information is available on the number of offspring/clutch. ("Atypus Affinis Purse-web Spider", 2010; Pedersen and Loeschcke, 2001)

  • Breeding interval
    These spiders breed yearly.
  • Breeding season
    Autumn
  • Average gestation period
    6 months
  • Range time to independence
    8 to 10 months
  • Range age at sexual or reproductive maturity (female)
    3 to 4 years
  • Average age at sexual or reproductive maturity (female)
    4 years
  • Range age at sexual or reproductive maturity (male)
    3 (low) years
  • Average age at sexual or reproductive maturity (male)
    4 years

Although their bodies are consumed by females, providing nourishment during gestation, males die before their offspring hatch, so females are solely responsible for parental care. Females suspend the egg cocoon within the tube of their web where it can be protected. After the offspring hatch, they remain in their mother's burrow for the better part of their first year of life. ("Summary for Atypus affinis", 2010)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Lifespan of female purse-web spiders is estimated to be approximately 8 years, with some living up to 10 years. Males often have shorter lifespans because they do not survive mating, which occurs as early as 4 years of age. There is no data available regarding the lifespan of this species in captivity. (Pedersen and Loeschcke, 2001)

  • Typical lifespan
    Status: wild
    4 to 10 years
  • Average lifespan
    Status: wild
    8 years

Behavior

Purse-web spiders are typically found in colonies, with 50 to 90 webs per square meter. Individuals dig their own burrows (which can be as deep as 90 cm) and line them with silk (the "tube" portion of the web). The silk extends along the soil surface where it is covered with debris. This portion of the web (the purse) is usually about 10 cm long and its horizontal positioning may be an adaptation for catching prey under snow cover. The web structure is described as being similar to the finger of a glove. The silk from which purse-web spiders build their webs is very strong, being comprised of a cysteine-rich structural protein, which makes it very strong. This species hibernates from November to early February. ("Purse-web spider (atypus affinis)", 2003; "Spider Webs", 2012; Pedersen and Loeschcke, 2001)

  • Average territory size
    10 cm^2

Home Range

The home range of this species is equivalent to its web size. (Pedersen and Loeschcke, 2001)

Communication and Perception

There is no specific data available regarding the communication methods used by Purse-web spiders. However, in general, web spiders often emit species-specific vibrational signals during courtship, which identify males. In spiders, the most common mechanoreceptors, used to perceive vibrations, are hair sensillum. All species of Atypus have eight eyes, which can be used to visually perceive their environment. (Folex, 2011)

Food Habits

This species is known to feed on beetles (Coleoptera), earwigs (Dermaptera), flies (Diptera), woodlice (Isopoda), and bees (Hymenoptera), relying on their webs to capture prey. Webs are disguised with soil particles on the surface of the ground and, when prey lands on them, spiders capture and kill the prey with their fangs and associated venom. The prey is then brought into the burrow and fed upon. Prey remains are thrown out of the tube. ("Purse-web spider (atypus affinis)", 2003; "Summary for Atypus affinis", 2010)

  • Animal Foods
  • insects

Predation

Purse-web spiders are the only known host of Aporus unicolor, a wasp which has a specialized foreleg for breaking into Purse-webs' webs. This wasp stings and paralyzes the web's inhabitant, laying an egg on it. The larvae then use the spider as food while they develop. Purse-web spiders are also prey to some other spider species, as well as birds and small mammals. ("Atypus Affinis Purse-web Spider", 2010; Falk, 1997; Newton, 2004)

  • Known Predators
    • Aporus unicolor (Family Pompilidae, Class Insecta)

Ecosystem Roles

Purse-web spiders act as a predators of insects and serve as a food source to other spiders, birds, and mammals, as well as the only known host of a spider-hunting wasp (Aporus unicolor), which stings and lays its eggs on the spiders. (Falk, 1997; Newton, 2004)

Commensal/Parasitic Species
  • Aporus unicolor (Family Pompilidae, Class Insecta)

Economic Importance for Humans: Positive

There is no specific information available on whether or not purse-web spiders affect humans positively; however, they do feed on pests that humans generally consider a nuisance. (Newton, 2004)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There is no specific information available on whether or not purse-web spiders affect humans negatively. However, they are a rare and typically shy species, so it is unlikely that they do.

Conservation Status

This species has not been targeted by most conservation groups, although it has been suggested that humans may adversely affect populations by trampling areas in which colonies have dug burrows and built nests. It is on the Red List in Denmark and Sweden, but not in the British Isles or other areas. ("Summary for Atypus affinis", 2010)

Contributors

Lama Bandar (author), University of Michigan-Ann Arbor, Jeremy Wright (editor), University of Michigan-Ann Arbor.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

semelparous

offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

2010. "Atypus Affinis Purse-web Spider" (On-line). Encyclopedia of Life. Accessed February 17, 2012 at http://eol.org/pages/732416/entries/36265286/overview.

2011. "Mysterious Purse-Web Spiders Rediscovered in South Africa" (On-line). USnews. Accessed January 20, 2012 at http://www.usnews.com/science/articles/2011/05/19/mysterious-purse-web-spiders-rediscovered-in-south-africa.

2003. "Purse-web spider (atypus affinis)" (On-line). Arkive-Images of life on earth. Accessed January 20, 2012 at http://www.arkive.org/purse-web-spider/atypus-affinis/#text=All.

2012. "Spider Webs" (On-line). britishspiders.org.uk. Accessed March 20, 2012 at http://wiki.britishspiders.org.uk/index.php5?title=Spider%27s_Webs.

2010. "Summary for Atypus affinis" (On-line). Britishspiders.org. Accessed January 20, 2012 at http://srs.britishspiders.org.uk/portal.php/p/Summary/s/Atypus+affinis.

Cressler, A. 2011. "http://dnr.wi.gov/org/land/er/biodiversity/index.asp?mode=info&Grp=22&SpecCode=ILARA08040" (On-line). Wisconsin Department of Natural Resources. Accessed January 20, 2012 at http://dnr.wi.gov/org/land/er/biodiversity/index.asp?mode=info&Grp=22&SpecCode=ILARA08040.

Cutler, B., G. Salsbury, H. Guarisco, C. Liggett. 2004. The Purse-Web Spiders of Kansas (Araneae:Atypidae). Transactions of the Kansas Academy of Science, 107/1/2: 101-104.

Falk, S. 1997. "Aporus unicolor Spinola, 1808" (On-line). Bees, Wasps and Ants Recording Society. Accessed September 14, 2012 at http://www.bwars.com/index.php?q=wasp/pompilidae/pompilinae/aporus-unicolor.

Folex, R. 2011. Biology of Spiders. New York, New York: Oxford University Press.

Newton, B. 2004. "Purseweb Spiders/University of Kentucky Entomology" (On-line). University of Kentucky. Accessed January 20, 2012 at http://www.uky.edu/Ag/CritterFiles/casefile/spiders/purseweb/purseweb.htm.

Pedersen, A., V. Loeschcke. 2001. Conservation genetics of peripheral populations of the mygalomorph spider Atypus affinis in northern Europe. Molecular Ecology, 10/5: 1133-1142. Accessed January 20, 2012 at http://onlinelibrary.wiley.com/doi/10.1046/j.1365-294X.2001.01266.x/abstract;jsessionid=7152F9871855D8F2555FEADAF44ECB61.d02t04.

Rezac, M., J. Kral, J. Musilova, S. Pekar. 2006. Unusual karyotype diversity in the European spiders of the genus Atypus. Hereditas, 143/2006: 123-129. Accessed January 20, 2012 at http://onlinelibrary.wiley.com/doi/10.1111/j.2006.0018-0661.01949.x/pdf.

Rezac, M., V. Rezacova, S. Pekar. 2007. The distribution of purse-web Atypus spiders in central Europe is constrained by microclimatic continentality and soil compactnes. Journal of Biogeography, 34/6: 1016-1027. Accessed January 20, 2012 at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2699.2006.01670.x/abstract.

Roberts, M. 1985. The Spiders of Great Britain and Ireland. Colchester, England: Harley Books.

Wolff, R. 2012. "Coye's Purseweb Spider" (On-line). South Carolina Department of Natural Resources. Accessed January 20, 2012 at http://www.dnr.sc.gov/cwcs/pdf/Pursewebspider.pdf.

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