Most aquatic spider

The only species of spider that lives almost entirely underwater is the diving bell spider (Argyroneta aquatica) of which large populations are found across Europe, northern Asia and North Africa. "Argytroneta" means "with a silvery net", and refers to the bubble, or bell, of air that the spider encapsulates itself inside and keeps attached to, using special hairs on its body. Although the spiders make infrequent trips to the surface to replenish the air, oxygen easily diffuses into the bubble from the surrounding water, and reversely, carbon dioxide diffuses out. All biological functions such as hunting (for shrimps), mating (after which the larger males often eat the smaller females) and laying eggs (inside water-tight nests within air pockets) occur underwater.

Unusually for spiders, the males are larger - typically weighing 0.15 g (0.005 oz) - whilst females weigh 0.10 g (0.003 oz) on average.