ART. 9 AMERICAN XYLOTINE SYEPHID-FLIES SHANNON 6 



genera in the tribe. The change in generic concept is based on a 

 character found on the metasternum. The tribe Xylotini may be 

 divided into six genera according to whether the metasternum bears 

 pile or is faintly pubescent or bare. Xylotivihna and Xylotodes 

 have the metasternum pilose; Xylota and Braxihypalpus have it 

 pubescent or bare. Supplementary characters are given in the 

 generic descriptions. It seems unfortunate to divide such well-known 

 genera as Xylota and Brachypdl'pus but in view of the method of 

 treatment for the Xylotini as given here, there would be only one 

 other alternative. This would be to make Syritta, Planes, Brachy- 

 palpus, and GaUiprohola, as well as Xylotomiina and Xylotodes, 

 subgenera of Xylota. In either case there would be the same number 

 of groups; and seeminglj^ the plan adopted is the better of the two. 



Hadromyia Williston was established for an American species, 

 grandis Williston, but was subsequently made a synonym by Willis- 

 ton of the European genus Pocota. Pocota hortibiforniis Hunter was 

 described at a later date. The latter is congeneric with Pocota api- 

 formis Schrank (genotype of Pocota). In both species the apical 

 cross-vein joins the third longitudinal vein at the very edge of the 

 wing; the head is small and narrower than the width of the thorax. 

 Hadroiivyia grandis differs noticeably in the wing venation and the 

 head is somewhat broader than the anterior of the thorax; further- 

 more the metasternum is normal in Hadromyia, but greatly reduced 

 in Pocota apiformis and homh&ides. Pocota {sensu strict o) appears 

 to be more closely allied to the Criorrhinini than to the Xylotini. 



Observations on certain Helophilini (Eristalinae) which were 

 described under Pterallastes are given in the discussion of that 

 genus. 



The tribe Xylotini is one of admitted difficulty. Confusion, in 

 some cases of a very great degree, exists among the majority of 

 the species, particularly in Xylota and Xylotomiina. Thirty-two 

 species of these two genera, five of which are new, are here definitely 

 I'ecognized. Forty-seven names have been previouslj'^ applied to 

 North American material, of which types and authentic specimens 

 of twenty-seven species have been examined. Of the remainder nine 

 are synonj-ms and nine Xearctic species have been transferred to 

 other genera. 



The examination of Walker's and Bigot's types produced several 

 suprising results. A number of well established names in modern 

 literature will have to give waj' to their names. The failure of the 

 attempts of Dipterists to unravel the species proposed by them prove 

 how untrustworthy are the generic locations and descriptions of 

 their species. 



The chief, confusion, aside from the misunderstanding of the 

 Walker and Bigot tj'pes, has come about through the use of color 



