Family: Thomisidae (crab spiders)

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

The Thomisidae, or Crab spiders are the masters of ambush and disguise. They range in size from 3-32 mm although they rarely exceed 11mm in body length. This large family includes 38 genera in South Africa and occurs on all continents except Antarctica. They are called crab spiders because of their crab-like appearance and sideways motion. They occur more commonly on plants, sometimes under rocks and are harmless to man.

The family name is derived from the Greek "thomis" means "a sting".

Genera indigenous to southern Africa

Ansiae

1 species.

 

Avelis

1 species.

 

Borboropactus

2 species.

 

Camaricus

3 species.

 

Cynathea

1 species.

 

Diaea

2 species. Very similar to Synema but without the mask on the abdomen. Diaea is derived from the Greek "dia" means "during" and "ea" means "spring"

 

Firmicus

2 species.

 

Heriaeus

5 species.

 

Heterogriffus

1 species.

 

Hewittia

1 species.

 

Holopelus

2 species.

 

Misumenops

1 species.

 

Monaeses

6 species.

 

Oxytate (grass crab spiders, green crab spiders)

5 species. Oxytate, previously known as Dieta, is long and slender and colouration varies from pale cream to translucent green sometimes freckled with lighter spots. The female's shape and colour afford effective camouflage among grasses and stems. Oxytate rests on grass with anterior legs outstretched forward and hind legs next to the body holding on.

Ozyptila

1 species plus 1 undescribed. Terrestrial.

 

Pactactes

3 species.

 

Parabomis

2 species.

 

Paramystaria

1 species.

 

Parasmodix

1 species.

 

Phaenopoma

1 species.

 

Pherecydes (stalky-eyed crab spider)

Phercydes with 5 species known from South Africa are long bodied and cryptically coloured in mottled greys, browns and black which affords camouflage on the bark of tree trunks. the eyes are on raised tubercles hence the colloquial name stalky-eyed crab spider. 

 

Phrynarachne

2 species.

 

Platythomisus

4 species.

 

Runcinia

8 species.

 

Simorcus

3 species.

 

Smodicinus

1 species.

 

Stephanopis

1 species plus one undescribed.

 

Stiphropella

1 species. Terrestrial.

 

Stiphropus

4 species. Terrestrial.

 

Sylligma

1 species.

 

Synema (masked crab spiders)

11 species. Synema has a green to brown prosoma (cephalothorax - anterior body segment including legs) and cream round to oval abdomen adorned with what looks like a brown skull. This colouration affords a good camouflage in vegetation. Synema is more active in its prey capture as it hides amongst the vegetation and dashes out to surprise an unsuspecting insect.

Talaus

1 species.

 

Thomisops

6 species.

 

Thomisus (flower crab spiders)

15 species. The most conspicuous genus in the family. Spiders are short and squat, ranging in size from 3-11mm. Sits next to flowers and ambushes insects just about to land on the flower. It is able to undergo white to yellow or pink colour changes depending on the flower it is sitting on. The first and second pairs of legs are noticeably longer and thicker than the last 2 pairs and are used for prey capture. The abdomen is triangular in shape, being widest posteriorly. The lateral eyes are situated on tubercles.

Tmarus (bark crab spiders)

Long-bodied and cryptically coloured in cream to brown mottled greys, browns and black which affords camouflage on bark. Tmarus rests on a twig with anterior legs outstretched forward and hind legs tucked in next to body holding on. A world wide genus with 9 described species and 1 undescribed in South Africa. 

Trichopagis

1 species.

 

Xysticus

9 species. Looks very much like Thomisus but with a round abdomen and no lateral eye projections. The dull brown colouration affords good camouflage for its more earthy lifestyle on the ground and under stones. Unlike Thomisus the male uses silk to secure the female to the substrate before mating. Ozyptila, Stiphropella, Stiphropus are other terrestrial genera.

Zametopias

1 species.

 

Publications

  • VAN NIEKERK, P. & DIPPENAAR-SCHOEMAN, A.S. 2010. A revision of the spider genus Simorcus Simon, 1895 (Araneae: Thomisidae) of the Afrotropical Region. African Entomology 18: 66–86.

Text and images by Norman Larsen


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