112 FLEAS, FLUKES AND CUCKOOS 



native flea from the hen roosts of North America — thus emulating the 

 unattractive behaviour of the human settlers from Europe. 



The biology of C gallinae has been studied in greater detail than that 

 of most other bird fleas. The life span of this species from ^gg to the 

 adult's death is on an average 450 to 500 days. As we have pointed out 

 on p. 69 this varies enormously according to the temperature and other 

 climatic conditions. The weather can affect the life-cycle in many ways. 

 For example, egg laying falls off in a very dry spell and so does the 

 proportion of fertile eggs laid. 



A nesting box used by blue tits was kept under observation after the 

 young had flown in June. Three months later the first specimens 

 of C. gallinae began to emerge and they continued to do so at intervals 

 until the following April. Thus, as the winter advanced, the fleas 

 remained for progressively longer periods in the larval stages. This type 

 of phenomenon has led some people to suggest that fleas can lay fertile 

 eggs in the absence of a mammalian or bird host and breed for several 

 generations in this manner. There is no evidence however, to support 

 this theory, which is pure surmise. On the contrary all the experiments 

 so far carried out go to prove the reverse. Not only does C. gallinae require 

 a blood meal before laying, but tgg production is confined to the spring 

 and early summer. 



C. gallinae is one of the species which has been observed leaving nests 

 in large swarms and as already stated, it is a great wanderer and found 

 in a variety of strange places far removed from a host or nest. We once 

 collected a specimen from a plate of soup in Plymouth. This was a 

 great surprise as most fleas found in such surroundings are cat fleas, 

 dog fleas and human fleas. 



Personally we have no great love for this species which has the 

 annoying habit of turning up in rare birds' nests, such as those of the 

 crested tit, or black redstart — even high up in the Alps — and thus 

 providing a series of disappointments for the collector who is hoping 

 for something new and strange. 



The crow flea is so like the hen flea that anyone can be excused for 

 mistaking one for the other. Unlike C. gallinae, however, C. rossittensis 

 is strictly host-specific and is confined to the crow [Corvus corone). It has 

 been recorded only once in Britain, from a nest in Cumberland, 

 although its presence here was long suspected owing to its distribution 

 in Germany and Holland. C. gallinae is the commonest flea in crows' 

 nests and as the two species are generally present in the same nest, and 



