Atypus affinis builds a tube of tightly woven silk, closed at both ends. Most of it lines a vertical burrow; the last several centimetres lie flat on the ground, disguised with grains of soil so that it resembles a root or a fallen twig.
The spider waits inside, resting against the wall. Vibrations from an insect crossing the surface section tell it where to strike, and its unusually long fangs pass through the silk and into the prey. It then cuts a slit in the tube, hauls the insect inside, and repairs the opening with fresh silk before feeding.
The arrangement conceals the animal almost completely. Purse-webs are found more often by pulling at a suspect tube than by seeing a spider, and populations can persist unnoticed on a single bank for many years, with females long-lived and dispersal limited to wandering males.