House fly  (Musca domestica)

Complete metamorphosis: type of insect development (also known as holometabolous development) in which there is a distinct larval and pupal stage. The larval stage is different to the adult in terms of both structure and diet, and the pupa is a relatively inactive stage in which the larval tissues are broken down and rearranged into adult structures.
Larvae: stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Pupal stage: stage in an insect's development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.

1. National Biodiversity Network Species Dictionary (March 2003):
   http://www.nhm.ac.uk/nbn
   
2. Sterry, P. (1997) Collins Complete British Wildlife Photoguide. Harper Collins Publishers Ltd., London.
   
3. Buczacki, S. (2002) Fauna Britannica. Hamlyn, London.
   
4. House fly (March 2003):
   http://www.oznet.ksu.edu/dp_entm/extension/InsectID/Mock/HOUSEFL.html
   
5. O'Toole, C (2002) The new encyclopedia of insects and their allies. Oxford University Press, Oxford.
   
6. Common house fly and lesser house fly. ADAS (March 2003):
   http://www.adas.co.uk/env/environment/pestmgt/Inverts_p114&5.pdf