Family: Selenopidae (wall crab spiders, flatties)

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

The Selenopidae are commonly referred to as wall crab spiders or "flatties" because of their dorsally flattened bodies. This family is named after the Greek moon goddess, Selene, due to the moon-like appearance of the eyes. These spiders are harmless to man.

Selenopidae are well represented in the Afrotropical region. They are nocturnal and free-ranging spiders and are well camouflaged on their usual habitat of rocks and trees where their flattened bodies enable them to retreat into small cracks and crevices. They are also common in houses where they are easily seen, usually inverted, on walls and other surfaces. Here they retreat to small crevices such as those behind skirting boards and picture frames.

Anyphops sp  

[image N. Larsen ]

 

There are two southern African genera, Selenops and Anyphops. Some species occur sympatrically (in the same area) but in different microhabitats (habitats with different environmental conditions e.g. one may be moist while the other will be drier). In the Kruger National Park one species was found to live on the ground while a second was found on the bark of pine trees.

Their broad flat, oval bodies are about 5-23 mm long and the legs spread outwards (latrigrade). They are cryptically coloured in cream to yellow or grey with mottled grey, brown or black markings and the legs are usually banded or mottled which may be distinct or indistinct. As with many spiders, their coloration varies and with the Selenopidae, the colouration can vary from one habitat to another, some resembling the lichen of their rock habitat or colour of the tree they occur on. These spiders do not have the ability to change colour but may result from a process of natural selection where those that did not blend in with the environment ended up as prey items. Selenopids normally appear sedentary and will stay motionless for long periods but they are able to move with great agility in a smooth flowing motion, their latrigrade legs enabling them to move rapidly in any direction. When moving normally their movement resembles that of the Sparassidae.

The eyes are arranged in two rows with the wide anterior (front) row of six eyes situated near the anterior edge of the carapace and the posterior row of two large eyes situated one on each side. In Selenops the four median form almost a straight row and with Anyphops they form a recurved row.

The smooth, papery egg sacs are disc-shaped and about 15 cm in diameter and are secured against the substrate.

These spiders are useful in controlling insect pests such as mosquitoes, moths and cockroaches. Research has shown that Selenops radiatus can be an effective controlling agent of the potato tuber moth in potato sheds in South Africa.

Genera indigenous to southern Africa

Anyphops

Anyphops occurs from Cape Town to Somaliland in north Africa and Madagascar with 56 species in South Africa. In Anyphops the four median eyes form a recurved row.

 

Selenops

Has a subtropical distribution occurring in central and south America, Asia, Africa, Mediterranean region of southern Europe. There are 12 species known from South Africa. In Selenops the four median eyes form an almost straight row.

 

Text by Norman Larsen


Contact us if you can contribute information or images to improve this page.

 Arachnids home   Biodiversity Explorer home   Iziko home   Search