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biodiversity explorer

the web of life in southern Africa

Genus: Caerostris (bark spiders)

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

Bark spiders are nocturnal orb-web spiders that construct a large orb web, up to 1.5 metres, stretching from one tree to the next. The abdomen is cryptically coloured and adorned with numerous horny projections and viewed from the rear a definite animal face can be perceived. When she is off her web she retires to a branch and packs her legs tightly next to her body and she melts into her surroundings looking like a knot on the branch. This spider is sometimes referred to as the Winston Churchill spider as in this position the abdomen with the two projections are reminiscent of a fist with fingers protruding in victory.

Caerostris are large spiders with females reaching 30mm in body length. Very few males, which are tiny, have been collected and no males are known for Caerostris corticosa.

Species indigenous to southern Africa

Four species have been reported from this region.

Caerostris corticosa

Caerostris corticosa occurs away from forest and appears to be an arid to fynbos species found in Botswana, the Northern and Western Cape with a record for Pretoria. At Grootvadersbos Nature reserve it was found to be common in burnt fynbos with webs spread between dead branches about 1.5-2metres above the ground. No spiders were found in the adjacent forest some 100-200metres away. It was not as common in unburnt fynbos. The egg sacs has a yellowish tinge and the spiderlings are black. The adult females were all a dark grey and no males are known.


Caerostris mitralis

Caerostris mitralis is found in Mozambique and Kwazulu/Natal in South Africa.


Caerostris sexcuspidata

Caerostris sexcuspidata, although nocturnal, can be found on her web in shaded forested areas during the day. This is the most widespread species occurring south of the 5 North (central and east Africa) It is the common species in South Africa and the species with the most variations in abdomen shape.

Caerostris vinsonii

Caerostris vinsonii.occurs from central Africa to Botswana, Mozambique and Kwazulu/Natal in South Africa.


Text and images by Norman Larsen .