(Argyroneta aquatica), an arthropod of the family Argyronetidae; the only representative of the order Araneida to live in fresh water. The body of the male is 15-20 mm long, the body of the female 12 mm. The cephalothorax is reddish brown, and the abdomen is covered with velvety hairs. When the water spider is submerged, these hairs retain a layer of air (for this reason the animal’s body appears silvery) which the spider breathes underwater (water spiders more often breathe through the skin than with the lungs).

Water spiders are common in Europe. They live in bodies of water rich in vegetation and feed on small invertebrates and insect larvae. The bell-shaped underwater nest is filled with air; the spider carries it on its body. The bell is held underwater by a web, with which the spider fastens the nest to vegetation. Here the spider eats its prey and reproduces; the female places a cocoon containing eggs in the bell and guards it until the young hatch.