^ 





INTRODUCTION. 



The principal object of the present Catalogue has been 

 to give a complete list of the specimens of Dipterous 

 Insects contained in the collection of the British Museum, 

 indicating at the same time the peculiarities of each, as 

 regards variations of character, locality, and the source 

 from whence it has been derived. With this view,, the 

 different individuals of each species contained in the col- 

 lection are indicated by the letters a, b, c, &c, following 

 the name of the species and its synonymes, and the de- 

 scription, if it appeared to have been before undescribed. 



This part of the Catalogue of Dipterous Insects has 

 been prepared and the new species described, by Mr. 

 Francis Walker, so well known for his attention to this 

 order of Insects. 



The remaining parts, containing the other families, are in 

 hand, and will follow as soon as they can be completed. 



JOHN EDWARD GRAY. 



British Museum, 



Nov. 19, 1848. 



