500 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 37. 



Article 26. Zoological nomenclature began with the year 1758. 



Article 27. "The law of priority obtains, and consequently the 

 oldest available name is to be retained." It further asserts that a 

 name, whether generic, subgeneric, or specific, founded on any part 

 of an animal, or of any of its early stages, is valid. 



Article 30. The type of any pol3^typical genus is that one of the 

 original species first designated as such type. An exception occurs 

 in those cases where the genus originally contained only two species, 

 neither of which had been designated the type by the founder of the 

 genus, nor by any subsequent writer, and an author later takes one of 

 these species as the type of a second genus, he thereby definitely 

 makes the remaining species the type of the old genus. 



Article 34. "A generic name is to be rejected as a homonym when it 

 has previously been used for some other genus of animals." Unless 

 the two names are identical, letter for letter, they are not homonyms. 



The following list contains all of the genera of Diptera known to the 

 writer as having been reported from North and Middle America up to 

 Januar}^ 1, 1909, together with their type-species and synonymy. A 

 few genera, such as those to which no species has ever been assigned, 

 and some others, founded on foreign species, are omitted in this list; 

 but as nearly all in this class are synonyms of older generic names 

 their omission in no way aflfects the status of the valid names 

 adopted in the present list. 



In the cases of those neglected, polytypical genera whose types 

 have not heretofore been designated, and which contain among their 

 original species one belonging to an older genus, such a species has 

 been selected as the type, thus, as far as possible, sinking tiiis class of 

 names into the sjmonymy. In this way, fewer changes have resulted 

 among the current names than would have been the case had the 

 opposite course been pursued. In selecting the types of polytypical 

 genera now in current use, it has been my constant aim to select such 

 a species as would result in the maintenance of the present status of 

 the genus. The recommendations appended to Article 30 of the 

 International Code, as amended at the 1907 (Boston) meeting of the 

 International Zoological Congress, have been essentially followed. 



The sj'nonyniy of the European species and, in most cases, the limits 

 of the genera, are those given in the moimmental Katalog der 

 Palaarktischen Dipteren, by Kertesz, Bezzi, Stein, and Becker, a most 

 admirable work, in four octavo volumes. Some idea of the magni- 

 tude of the labors of its authors in unraveling and recording the 

 greatly involved synonymy may be gleaned from a few facts relating 

 to a single species, Tachina vulgaris Fallen. This species has been 

 redescribed and renamed no less than two-hundred and fifty-seven 

 times! On this one species alone Robineau-Desvoidy established the 



