Purse-web spider  (Atypus affinis)

Information authenticated by Dr Peter Merrett of the British Arachnological Society:
http://www.britishspiders.org.uk/index.html

• Abdomen: in arthropods (crustaceans, insects and arachnids) the abdomen is the hind region of the body, which is usually segmented to a degree (but not visibly in most spiders). In crustacea (e.g. crabs) some of the limbs attach to the abdomen; in insects the limbs are attached to the thorax (the part of the body nearest to the head) and not the abdomen. In vertebrates the abdomen is the part of the body that contains the internal organs (except the heart and lungs).
• Carapace: the top shell of a turtle. In arthropods (insects, crabs etc), the fused head and thorax (the part of the body located near the head) also known as ‘cephalothorax’.
• Chelicerae: pair of appendages on the ‘head’ of an arachnid (spiders, scorpions, mites, harvestmen etc). In spiders and harvestmen these appendages are jointed and are used to kill prey, and in defence. In spiders there is a poison gland at the base of each chelicera, from where a duct leads to the tip of the fang.
• Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

1. National Biodiversity Network Species Dictionary (September 2003) http://www.nhm.ac.uk/nbn/
2. Roberts, M.J. (1993) The spiders of Great Britain and Ireland Part 1- text. Harley Books, Colchester.
3. Roberts, M.J. (1995) Spiders of Britain and northern Europe. Harper Collins Publishers Ltd. London.