PKEFACE. 



This preliminary list of Durham Diptera has extended to a 

 far greater length than I contemplated when I wrote the 

 introduction. In Mr. Verrall's list of the British species, 1901, 

 there are 2884 names. The following pages contain some 

 guide to the specific characters of 2210 of these. Three 

 families with 390 species are not touched specifically at all, 

 and 284 other species are omitted whose characters I have not 

 been able to discover. But 318 European species are added, 

 some of which have been found, and others may yet be found 

 in Britain. Altogether, characters more or less satisfactory 

 are given for 2526 species, and localities for 626 of these which 

 I have found in our district. 



Well do I know how such tables may easily lead a novice 

 far astray; but carefully and cautiously used, I hope they may 

 be the means of enabling some to make a start with the Flies. 

 It does seem strange, that what I may call our ' Domestic 

 Insects ' should receive so little attention, that very few, even 

 among entomologists, can point out with any certainty the 

 common House-fly or distinguish between the Blue-bottles. 

 As Schiner well remarks, " niemand kiimmert sich um 

 diese unscheinbaren Graujacken " — no one troubles about 

 these insignificant grey-jackets. And yet no order of 

 insects has so many interesting and varied life histories, 

 and none so deeply affects the human race, whether as 

 protectors when acting the part of scavengers, or depre- 

 dators destroying the crops, or scourges carrying the deadly 

 micro-parasite. If some of our members will only start 

 to examine and collect the denizens of their windows, and 

 with the help of the following pages get a knowledge of 

 their parts, and more or less correctly identify the species, I 



