04 November 2012

Fishing Spider - Dolomedes sp. A (undescribed)

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Fishing Spider - Dolomedes sp. A (undescribed)

I discovered this handsome fishing spider under an exposed rock in the middle of a small creek. The rock (a piece of limestone) was resting on a couple of other limestone rocks with water continually running over them, after rain all rocks would probably be submerged. The spider had a small web-lined retreat and likely remained there during floods and as can be seen by its very hairy state, would trap air around its body to enable it to breathe underwater.

This is the only individual of this species encountered, but as the creek has many areas of exposed limestone, it would probably be found elsewhere along the waterway. The body length was a little over 2 cm (nearly 1") with a total span of around 8 cm (over 3"). Such water spiders can not only walk on water, but swim under it too, where they hunt small fish, tadpoles and aquatic invertebrates.

There is another fishing spider in the area (that I shall detail next), which is more common, less hairy and can also be found well away from water. Apparently this other species is the only Dolomedes recorded for WA. The Giant Water Spider, Megadolomedes australianus is also found in WA, but this species although larger has much longer/finer legs and is also less hairy (I have not encountered this species in the Esperance region).