Red and Black Spider
Ambicodamus crinitus
Family: Nicodamidae ID: Koch, 1872

Habitat and Biology 
  In summer, males leave their web, during daylight hours, 
  and wander in search of females. This wandering habit often brings them indoors. 
  Due to the red and black colour, the spider is often confused with the red-back 
  spider and, as red is a common warning colour, the spider is sometimes thought 
  to be highly venomous. The egg case has a woolly appearance and is suspended 
  in the web. 
Colour
  Male: Similar to female.
  Female: Body and legs commonly bright red, abdomen 
  black, but varying orange to dark red, sometimes with a bluish tinge.
Form
  Typically a small spider with slender legs, most easily recognised 
  by colour pattern as described above.
Body Length
  Male: 10mm
  Female: 12mm
Web type
  A few irregular strands built under bark, stones or logs.
Bite
  Despite the red colour of this spider its venom is not dangerous. 
  At most, it may cause a local reaction around the bite site. Normal precautions, 
  as outlined in the introduction, should be observed.