

\vv 

 A CATALOGUE OF 



NORTH AMERICAN DIPTERA 



BY T. M. ALDRICH. 



INTRODUCTION. 



The present work is based upon Osten Sacken's Catalogue of 

 North America Diptera, second edition, published in iS/S.* All the 

 references of that work are embodied in this, with only such changes 

 as later studies seem to require. 



Still, the great amount of work which has been done on North 

 American Diptera within the quarter of a century has largely changed 

 the face of the subject. Hence the reader will probably observe, 

 especially at first, more of contrast than resemblance. The number 

 of species has doubled ; the number of references to previously known 

 species has almost doubled ; several families have been monographed 

 or revised, with more or less change of nomenclature ; along with this 

 has gone the publication of a multitude of smaller papers, touching 

 every family but one, and the larger part of the genera. Under these 

 conditions it is inevitable that great changes should appear in the new 

 catalogue. It is the more necessary that I should acknowledge my 

 obligation, which is far greater than appears on the surface. 



Faunal limits. These, as in the former catalogue, include all of 

 North America, in the widest sense, taking in Panama on the South 

 and Greenland and the Aleutian Islands on the North. The West 

 Indies are included, even down to Trinidad, adjoining Venezuela. 

 There is no place to draw a line between the islands. The Bermudas 

 and the Hawaiian Islands are not included. 



Scope. To give the most information consistent with the limits 

 of space has been the object. All references to a species, if in any 

 way descriptive or useful, have been inserted if found. The only 

 known exceptions are in those species like the Hessian fly and house- 

 fly, where the references are so numerous that a selection of the more 

 important articles is necessary. Another exception is uniformly made 

 of articles in non-scientific journals ; these are only mentioned when 

 of importance in tracing the history of a species. 



* Smithsonian Miscellaneous Collections, Vol. xvi. 



