While thrashing in a woodland pond on my work experience, one of my thrashings brought up an adult diving bell spider. These peculiar spiders live among reeds and weeds in ponds from Asia to Europe, including British ponds. They are the only type of spider to live their entire life under the water, in little web ‘diving bells’ containing air. In well oxygenated water, new oxygen will diffuse down the concentration gradient into the diving bell, removing the need for the spider to ever return to the surface to collect more oxygen. This means the spider will hunt and mate within the safety of these bells, without ever having to leave. They hunt mainly small invertebrates and crustaceans, such as nymphs and fresh water shrimp, which they dart out of their bells to catch.
This particular spider is a female, which can be seen by her small size and dark colouration. Unusually for spiders, the female is much smaller than the male, who has a far more active life of hunting then the female. A male also has much lighter yellowish colours and creates far smaller bells to live in. When the spiders want to mate, the male will build a new bell near the female’s bell, and will then weave a tunnel through into the female’s area, where they will mate. Typically 40 – 50 eggs are lain, and will hatch into baby diving bell spiders, most of which will be eaten by frogs and fish.
Rather than release this spider back into the pond, Matt took it with him, since a friend of his had been looking to keep one. They are fairly challenging to keep, requiring live prey, large spaces, and well oxygenated water. These are not recommended for beginner keepers.