242 Messrs. A. D. Hobson and L. H. Matthews on the 



It will be noted tliat some forms fall into more than one 

 group at different stages in their life-history. Such an 

 animal is the pigeon-flea, of which the larva feeds on refuse 

 in the nests, whilst the adult is a parasite. ^ 



The following list includes all the members of this associa- 

 tion which have so far been obtained. It is by no means 

 complete, owing to the difficulty of collecting material 

 because of the minute size of many of the animals. Indeed, 

 additional species are continually turning up. 



Mammalia. 

 Barbastella barhastellus, Gm. Barbastelle Bat. 



The only mammal hitherto found. A single specimen was 

 obtained from a crevice in the rafters on October 7th, 1922. 

 This, incidentally, is the second recorded occurrence of this 

 bat in Cambridgeshire. 



A V E s. 



Columha livi'a. Pigeon. 



Ecologically this is the most important animal, most of the 

 fauna forming a " pigeon association '^ around it. 



Mollusc A. 



Helix arhustorumj L. 



A single living example and one empty shell were taken 

 in a dark part of the roof-space in August. This is the most 

 anomalous member of the fauna, it being difficult to find any 

 explanation for its presence owing to lack of suitable food. 



Arachnid A. 



Araneina. 



Spiders are numerous in all parts, but, so far, have not 

 been identified. There is reason to believe that they feed, in 

 part at least, on the inhabitants of the pigeon refuse. 



Chernetidea. 



C hemes sp. 



One specimen only was found in rubbish. It is predaceous 

 on refuse-feeders. 



