AUTHOR'S PlIErAOE. 



The present volume, which deals with the Indian Nkmato- 

 CERA,* except the Chironomid^ and Culicid.e, is the first one 

 of the ''Fauna of British India'' series devoted to the Diptera, 

 although this is an order of insects abundantly represented 

 in every region of the globe, excepting only extreme arctic lati- 

 tudes and torrid deserts, and even in these latter parts more 

 species are to be found than might generally be sup[)Osed. 



Yet the study of Oriental Diptera is quite in its infancy, 

 less than 3000 species being known from the whole region as- 

 late as 1896. Since that date certain groups have been revised, 

 but the material thus treated has, in nearly every case (except 

 the mosquitos), been drawn from but a limited section of 

 that zoological region. The Culicid.e is the only family that 

 has been extensively studied from any considerable number 

 of localities within the limits of the "Fauna'' series. 



It would not be unreasonable to estimate the existing 

 species of the more conspicuous families (such as Tabanid^,. 

 BoMBYLiiD.ii:, AsiLiD^:, Syrphid.e, and the more showy 

 Muscid/e) at not less than double the number of those 

 already recorded ; whilst in the more obscurely coloured 

 groups (as, for example, the Chironomid^, MvcEToPHiLiDiE,^ 

 EMPiD.^i:, and the more sombre Muscid^e), the existing 

 species may outnumber the known ones by many times. 

 The MusciD.E are mainly obscurely coloured or else the 

 species are very difficult to differentiate, which probably 

 accounts for the general neglect of this family. Yet the 

 family contains about a third of all known Diptera. 



* [The author has used the word Nemocera throughout his manu- 

 script, but it has seemed advisable to adopt the more correct form, 

 Nematocera, which is now more generally used by dipterologists. — Ed.] 



