THE CANADIAN ENTOMOLOGIST 35 



to raise what he rightly calls the "virtual blockade" in this group. 

 The chief object of the author has been to make the species recog- 

 nizable and their determination as easy as possible. To this end 

 he has subordinated the desire so frequently prevalent among 

 certain systematists to create a large number of genera. Had he 

 not been conservative in .this respect there is little doubt that no 

 one but the author would have been able to recognize the genera. 

 The author's remarks on this aspect of the subject will find much 

 sympathy among working entomologists. He says: "A survey of 

 the present status of the Muscoid Diptera indicates unmistakably 

 that our great need is net mere genera, but a more complete 

 knowledge of species. The tendency of extreme generic specializa- 

 tion is to erect about itself impenetrable barriers of names, as is 

 well illustrated by Desvoidy and Bauer. Genera conceived in this 

 mental atmosphere are likely to be almost wholly subjective 

 creations, which make no impression on the minds of others. The 

 argument that the classification must express the relations has its 

 dangers, partly from the subjective elements involved, and partly 

 from the fact that the classification has also another important 

 function — to provide us with names for our species, which should 

 be as stable as possible if they are to have any usefulness. Further- 

 more, to separate a species from the genus in which it has been 

 located expresses one relation, that of difference; but it obscures 

 another, that of resemblance, which may be more important. One 

 of the main objects of the present work is to make the identifica- 

 tion of species as simple and certain as possible, and thus to attract 

 biological and economic workers to the group. This object would 

 inevitably be defeated by the erection of a considerable number of 

 separated genera. These are the governing considerations which 

 have prompted the preservation as nearly as practicable of the old 

 genus Sarcophaga." 



The species are separated on the characters of the genitalia 

 which method of separation in this group was first employed by 

 Parker in his study of the Sarcophagidae of New England. The 

 taxonomic value of the genitalia in difTerent groups of insects, such 

 as Diptera, Coleoptera, Lepidoptera and Mallophaga, is now being 

 clearly demonstrated b^' different workers, and a valuable and 



