62 DIPTERA OF NORTH AMERICA. 



of the globe. Among the former there are some, which are avail- 

 able or may be rendered available by removing the aberrant species 

 from them ; the remaining genera either have no claim to the names 

 of genera, or are understood by different authors in so different a 

 sense as to render their adoption more perplexing than useful. 

 But a few of the available genera are represented in North Ame- 

 rica. The genera created for single species have usually been 

 established on account of a single striking character, no informa- 

 tion being given about the other characters ; so it will be next to 

 impossible to place new species in such genera without incurring 

 the risk of gross mistakes. 



Such being the case, I will be justified, I think, in comprising 

 all species under the head of Trypeta, in the sense of Meigen and 

 Wiedeinaun. I should be glad indeed if by the communication of 

 numerous species I was enabled to divide the N". A. Trypetina 

 into smaller genera. To obtain numerous species is only possible 

 by breeding them, which is a very easy task ; for the larvae are 

 easily discovered ; they live in stalk-galls, or in berries and berry- 

 like fruits ; but most frequently in the flower-heads of Composites, 

 among which they prefer the Cynarocephalce to all others. 



To prevent any misunderstanding I finally have to observe, that 

 in the following descriptions, by the length of the borer I always 

 meant the length of its first joint only, which is also comprised in 

 the indication of the length of the females. The length of the 

 whole borer depends so much on the more or less extension of its 

 three segments, that no certain measure of it can be given. 



Synopsis of the species described in the sequel.* 



, ( Wings pictured (reticulate or banded). 

 I Wings not pictured, hyaline. 26 



( Wings banded. 3 



~ i 

 (. Wings reticulate. 15 



( Third longitudinal vein with bristles. 4 



( Third longitudinal vein without bristles. 10 



, ( Abdomen black. 1 discolor, n. sp. 



1 Abdomen yellow. 5 



* If a species is not found among those enumerated in this synopsis, 

 before pronouncing it to be new the Appendices I and II should be con- 

 sulted. This table contains only species described from specimens, and 

 not merely quoted from other works. 0. S. 



