Family: Selenopidae (wall crab spiders, flatties)
(animals) > Bilateria > Ecdysozoa > Panarthropoda > Tritocerebra >
Arthropoda > Arachnomorpha > Cheliceriformes > Chelicerata > Euchelicerata
> Arachnida > Araneae
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
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
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
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 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
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
Text by Norman Larsen ©