Cheiracanthium mordax
Family: Miturgidae ID: Koch, 1866

Habitat and Biology 
  The sac spider is another vagrant hunter. It makes a silken 
  retreat or sac in which it rests during the day and may be used for moulting 
  and egg laying. In nature, the spider's sac occurs under the bark of trees or 
  amongst foliage. In buildings, the spider's sac is built behind cupboards, pictures 
  etc. The egg mass is deposited in the sac, encased in silk and guarded by the 
  female. The lifespan is not known but is unlikely to exceed two years. 
Colour
  Male: Similar to female but often slightly darker overall.
  Female: Cephalothorax and legs pale brown, abdomen 
  cream with darker longitudinal stripe on upperside.
Form
  Small, stout-bodied spiders with slender legs; male has remarkably 
  enlarged jaws giving it a rather unusual appearance.
Body Length
  Male: 9mm
  Female: 10mm
Web type
  Does not build a web.
Bite
  The bite of this spider may cause general symptoms including 
  local pain and ulceration, nausea, faintness and headache.