Genus: Thalassius (fishing spiders)

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

The Fishing spiders belong to the genus Thalssius, a group of large to very large spiders (15 to 30 mm). The more plainly marked spiders very superficially resemble the rain spiders, Palystes but the latter has banding under the legs and a white clypeal stripe. Thalassius is very variable in colour ranging from olive brown without markings or reddish to dark brown with the typical cream lateral bands or cream speckling and no banding with various colour forms occurring in the same species in the same locality. 

Thalassius is always associated with water and appears to be both diurnal and nocturnal often retreating amongst vegetation by day. It can be seen resting on the water surface waiting for prey with its hind legs anchored on a leaf or rock or with its entire body on the water anchored to the shore with only a silk thread. The surface tension of the water prevents the spider from sinking. When it detects vibrations of passing prey such as fish, tadpoles, frogs and other invertebrates, it dives into the water and after much splashing the spider emerges from its wrestling match with its prey held under its body. It then retreats to a quiet spot in the vegetation or on a rock to consume its prey. These spiders can be voracious feeders as one was seen to consume two Rana tadpoles, both larger than the spider, within 24 hours.

Thalassius' integument (body covering) has a waxy coating that allows it to remain dry.

Thalassius sp. [image N. Larsen ] Thalassius spinossissimus with a tadpole. [image N. Larsen ]

Thalassius spinossissimus with a tadpole. [image N. Larsen ]  

Text by Norman Larsen

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