Water spider  (Argyroneta aquatica)

Water spiders spin underwater retreats amongst the weeds which they fill with air by travelling up to the surface and returning to the retreat, carrying air bubbles around the body (2). As they fill with air, these retreats become bell-shaped and take on a silvery sheen. The scientific name of this species Argyoneta derives from the Latin for silvery net, and refers to this unique air-bell that the species creates. Amazingly, the spider does not have to replenish the air-supply in the bell very often, as oxygen diffuses in from the surrounding water and carbon dioxide diffuses out (7).

This species is largely solitary, holds an exclusive territory and is mainly active at night. Males tend to be more active then females and actively hunt their prey. In contrast, females spend most of the time inside the air-bell and catch prey that strays too close to the bell (3). Prey species include small aquatic invertebrates such as water boatmen and tadpoles (1).

Males will mate with females after building an air-bell next to that of a female. He then bites through and mates with the female. The female spins a cocoon around the eggs at the top of her air-bell. The young spiders hatch after a few weeks and disperse (1). Before hibernating, water spiders seal up their air-bell or occupy an empty shell, which they line with silk (1).