Stegodyphus lineatus

Taxobox
name = "Stegodyphus lineatus"

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image_caption =
image_width = 250px
regnum = Animalia
phylum = Arthropoda
classis = Arachnida
ordo = Araneae
subordo = Araneomorphae
familia = Eresidae
genus = "Stegodyphus"
species = "S. lineatus"
binomial = "Stegodyphus lineatus"
binomial_authority = (Latreille, 1817)
range_

range_map_width = 250px
synonyms ="Eresus lineatus"
"Eresus acanthophilus"
"Eresus unifasciatus"
"Eresus adspersus"
"Eresus fuscifrons"
"Eresus lituratus"
"Stegodyphus adspersus"
"Stegodyphus molitor"
"Eresus arenarius"
"Stegodyphus quadriculatus"

"Stegodyphus lineatus" is the only European species of the spider genus "Stegodyphus".

Description

Males are up to 12 mm long, females up to 15 mm. The colour can range from whitish to almost black. In most individuals the opisthosoma is whitish with two broad black longitudinal stripes. Males and females look similar, but the male is generally richer in contrast and has a bulbous forehead.Bellmann 1997] The species name refers to the black lines on the back of these spiders.

Behaviour

These spiders build a web between twigs, mostly of low thorny shrubs. The web has a diameter of about 30 cm and a retreat of about 5 cm, which is open at the bottom. The spiderlings are hatched in this retreat, being released from their cocoon by their mother and then protected by her for a further two weeks. Adult males can be found in spring.

Offspring are "matriphagous" meaning they eat their own mother. Females therefore gain no advantage from further matings with other males. This is not the case for males, however, who chance upon only one or two mates in their entire lifetime. Egg sacs are naturally lost quite frequently, and females are able to lay another clutch if they lose their first. This represents an opportunity for males, however, who can secure themselves a mate by simply disposing of her offspring (this can occur because some males are still seeking mates when most females have already laid). Males go about this by detaching the egg sac with their chelicerae, moving it to the entrance, then simply tossing it to the ground.Schneider & Lubin 1996]

This behaviour, known as infanticide, is not so straightforward for males however. Female fitness is greatly reduced by the loss of their young, with the female being less likely to survive until her next lot of offspring can hatch, as well as having less eggs the second time. Their offspring also hatch later in the season and are less likely to thrive themselves. With this in mind, it comes with little surprise that females aggressively attend to their nest, chasing off around half the males that come nearby. Males can sustain injuries in these battles with the larger females, and in some cases the females not only kills, but eats the male intruder. For males however there is little option but to take this risk, resulting in a case of sexually antagonistic coevolution that sees around 8% of egg sacs destroyed.Arnquist & Rove 2005]

Distribution

"S. lineatus" occurs in Europe only in the southern Mediterranean region (south of Barcelona, southern Greece including Crete) and stretches up to Tajikistan.

Footnotes

References

* (1996): Infanticidal male eresid spiders. "Nature". 381: 655-656.
* (1997): Kosmos-Atlas Spinnentiere Europas. "Kosmos". ISBN 3440107469
* (2005): "Sexual conflict". Princeton University Press, Princeton ISBN 0691122172