The single species of this genus is widespread in the
palaearctic region, (this includes Europe and northern Asia, together
with Africa north of the Sahara). This is the only spider known to live
permanently underwater. The spider can swim with ease and constructs
an inverted retreat which it fills with air. This is accomplished by
trapping air on the abdomen. The air is collected from the surface with
a flick of the rear legs. At the retreat the air is brushed off, several
journeys are required to fill the "bell". Prey is taken to
the retreat for consumption, although rarely it may be taken to the
surface.. Moulting also takes place at the surface, or at least in the
vegetation above it.. This would seem to be necessary for the cuticle
to harden although moulting has also been observed within the bell.
Courtship by the larger male is rudimentary but, as
in other genera of this family, the couple seem to spend a lot of time
together. The eggs are laid in late spring and summer; they are surrounded
by a thick white silk which is placed in the top of the cell. In the
late autumn the spider thickens the silk of it's retreat and seals itself
up in the bell for the winter.
The female size ranges from 8 - 15 mm and the male is
9 - 12 mm, in a lot of cases the male is bigger than the female.
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