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Life in Freshwater

Water Spider (Argyroneta aquatica)

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Water Spider

IDENTIFICATION: The fact that the spider lives under water is a good indication of the species name. It is a pale brown on the cephalothorax and the abdomen colour is dark. However it is difficult to see the colour as the fine coating of hairs produce a neat covering of air. The legs have a sparse covering of spiny hairs. This spider is widespread across Europe although not so abundant in the south. Common in the UK. The Water Spider is the only spider capable of living permanently under water and requires a well vegetated pond. It can be found in moving water but only if the flow is slight.

ECOLOGY: This is a very successful spider and spins a web under the water across the vegetation. It swims with an ungainly movement to the surface and collects air on the velvet hairs of the abdomen, trapping it there with the hind legs. Then it clambers down, under the web and using the legs scrapes the air bubble off the body. In this way the web takes the shape of a bell under the pressure of the air bubbles which soon fill it. Within the bell the spider lives, mating and taking the food in there to eat. It feeds on a variety of aquatic animals although the Water Hoglouse (Asellus) is the main prey. Many strands of web are produced around it so that it can pull itself along with the air bubble on its back. The bell acts a little like a gill: some of the carbon dioxide diffuses out into the water and oxygen diffuses into the bell of air. However, the spider does have to replenish the bubble occasionally. During the autumn the web is thickened and they hibernate here. The male may share the bell with a female and the eggs are laid here where they hatch. Once they leave the bell they do not make their own bell immediately but are somewhat nomadic as they disperse. During this time they may use old snail shells which the fill with air. In this way they can spend almost their entire life under water even though they still breathe air!

See also the Raft Spider

Water Spider (Argyroneta aquatica)










Aranae - spiders

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