THE DIPTERA OF CAMBRIDGESHIRE. 



By JAS. E. COLLIN. 



THE Diptera are for many reasons by far the most difficult 

 Order to deal with in making a complete account of the 

 characteristic fauna of any particular county, and Cambridge- 

 shire is no exception to the rule. 



The number of collectors of Diptera in England is very 

 small, and those who study them may almost be reckoned on 

 the fingers of one's hands, while the number of those who 

 have correctly named their captures and published any Lists is 

 smaller still; consequently our knowledge of the distribution 

 of species in England is very slight, and a species may have 

 been considered local, or rare, merely because it has never been 

 collected, or if collected has not been named and recorded, 

 from any other locality. It is very probable that the species 

 of Diptera are more widely distributed in England than any 

 other Order and that it is only a question of looking for them 

 in the right places. 



In this account of the Cambridgeshire Diptera it is pro- 

 posed to divide the county into two districts, viz. : 



1. The Northern or Fen District; including practi- 

 cally all that part of the county north of Newmarket and 

 Cambridge. 



2. The Southern District. 



By this means we make it easier to refer to those Diptera 

 occurring in the Fens, among which there is greater pro- 

 bability of species being confined to Cambridgeshire only, or 

 occurring in numbers in that county and rare elsewhere, 



