Stegodyphus (social spiders)

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Ecdysozoa > Panarthropoda > Tritocerebra > Arthropoda > Arachnomorpha > Cheliceriformes > Chelicerata > Euchelicerata > Arachnida > Araneae > Araneomorpha > Family: Eresidae

Stegodyphus, commonly called social spiders, occur in Africa and South America with 8 species occurring in South Africa. This genus has the typical Eresidae feature and the colour varies from shades of grey to brown with black markings and yellow infusions. The flat face has 2 contiguous (so near that they touch) black triangular markings meeting medially. Females of the social species are 8-14 mm in length and males slightly smaller. Spiders of the solitary species are normally larger, ranging from 6-23 mm in length.

Most species are solitary except the social Stegodyphus domicola that occurs in most of southern Africa, and Stegodyphus mimosarum that occurs in the eastern regions. The latter two species are the most commonly encountered resulting in the misleading common names, community nest or social spiders, being used to describe the entire genus.

Stegodyphus could in fact have been called the tennis net spider due to its hackle web that is stretched between two points. The hackled appearance is due to the cribellate (teased) silk used. At one end of the web is a small ball-shaped nest attached to the vegetation, about a metre above the ground. In the Western Cape these webs are found in the Fynbos while in the Bushveld, the Acacia trees are used. However, fences, poles and other structures are also used. A new nest is started by as few as two spiders (usually female) that leave their original nest. As the colony increases, the nest is enlarged by successive generations. The nest includes mostly female and young; the latter living in chambers within the nest, much like a block of flats. The nest can be used for many years and can house in excess of 100 spiders. Birds often use the silk to line their nests.

 

The above photographs of a Stegodyphus sp. nest  were taken by Dr VB Whitehead in November 1977, 23 km NW of Onseepkans, Namibia.

There is a variation of adult size as Stegodyphus mature at different moult stages ( 7 to 10 stages) and adults continue to moult even after maturity. Mature spiders in smaller colonies tend to be larger than mature spiders in larger colonies.

Stegodyphus sp. Stegodyphus sp. with wasp prey.

When prey lands in the web, a few spiders rush out, overpower and collectively drag it to a nest chamber where they will be joined by other spiders for the feast. The larger the prey, the larger the number of spiders that assist with its capture and removal.

 

Text by Norman Larsen .


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