SOCIAL SPIDERS (Stegodyphus)

 Part of the large web of Social spiders in my garden

A couple of years ago I watched with amazement as a rather large spider web, stretched between two plants in my garden, evolved into a HUGE, messy mass of webs that contained hundreds of small, rather crab-looking, grey spiders. 

At first I wasn't sure whether I should allow this or not, that corner of my garden started looking like something out of a horror movie, with entire plants being enveloped by huge nests. But after days of observation, I was entranced by the fact that the nest was filled with dozens of spiders and that they seemed quite happy living in such close proximity with one another. 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. It was awesome to watch!

 Social spiders in my garden capturing prey

Upon further investigation, I discovered that they are Stegodyphus, commonly called social spiders, occurring 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. 

Most species are solitary except the social Stegodyphus domicola that occurs in most of southern Africa. 

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 meter 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. 

Pic from BiodiversityExplorer

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 or even thousands of spiders. Birds often use the silk to line their nests. 

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