EUROPEAN AND AMERICAN FAUNA COMPARED. 333 



Sonchus) and Tephritis angustipennis (occurring in Europe on 

 Acliillea ptarmica). The specific identity of the American. 

 Acidia fratria and the European Acidia heraclei is not impossi- 

 ble, although as yet not certain. 



It must be borne in mind, however, that all the comparative 

 statements, given above, are founded upon a very imperfect 

 knowledge of the North American fauna, and may be considera- 

 bly modified with an increase of this knowledge. 



If the European Trypetina be compared, not with those of the 

 whole North American continent, but with the fauna occurring 

 in America within the European latitudes, then some of the more 

 striking differences between the two faunas at once disappear, as 

 those subgenera which are absolutely foreign to Europe (Hexa- 

 chseta, Acrotoxa, Blepharoneura, and Acrotaenia) do not reach 

 so far north. The occurrence of all four of these subgenera in 

 Brazil proves that they are South American forms, which extend 

 to the southern portions of the North American continent. 



It was to be expected that the knowledge of the North American 

 species should exercise an influence upon the subdivision of the 

 old genus Trypeta in subgenera, a subdivision hitherto based 

 almost exclusively upon European species. Those North Ame- 

 rican subgenera, which have no relationship whatever to Euro- 

 pean forms, of course merely increase the number of subgenera, 

 without influencing in any manner the already existing subdivi- 

 sion. But it is different with those subgenera which contain 

 forms common to both continents, and here the modifying influ- 

 ence of the American fauna becomes apparent. Thus we can 

 already recognize : 1. That the definition of the subgenus Car- 

 photricha, founded upon European species, has to be modified, 

 in order to include all the species belonging to it; 2. That the 

 genus Oxyphora, in its present acceptation, contains, besides a 

 number of closely allied species, several far too aberrant forms ; 

 moreover, that it can no more be separated from the neighboring 

 subgenera merely by the presence of bristles upon the third vein, 

 a character which hitherto has been found sufficient for the dis- 

 tinction of the European species ; 3. That the subgenus Ensina 

 must, be taken in a broader sense than has been- done in my 

 Monograph of the European Trypetse, especially through the 

 addition of some species which, in the same Monograph, were 

 placed in Oxyna; 4. That the remaining portion of Oxyna 



