2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 60 



The Xylotine tribe of Syrphidae is characterized by a dorsal arista 

 on a usually suborbicular third antennal joint ; face more or less flat 

 or raised to a median keel, in profile ranging from straight to con- 

 cave ; epistoma truncated ; face bare except for sparse hairs along eye 

 margins; marginal cell open; discal crossvein joining discal cell 

 at or beyond its middle, rarely before ; hind femur usually enlarged, 

 frequently greatly swollen, and spinose along lower surface; body 

 without black and yellow wasplike markings; males with protuber- 

 ances on hind legs, which may occur on metasternum, trochanters, 

 femora, or tibia, very rarely on coxae; males with only four visible 

 abdominal segments. 



The name Xylotini and the definition of the tribe has been used 

 in rather a broad sense in order to include Teuchocnemis^ Ptercdlastes^ 

 Tropidia^ Syntta^ Xylota, Brachypalpus^ Galliprohola, and Pocota. 

 Four additional genera are also recognized and included in the North 

 American fauna : Xylotomima^ new genus {Xylota^ in part) ; Xylo- 

 todes^ new genus {Brachpyalpus^ in part) ; Hadrotnyia Williston 

 {Pocota^ in part) ; Planes Rondani {Syritta, in part, tropical). 



The South American genera consist of Tropidia {OrtholopTms 

 Bigot), Acrochordonodes^ Stilbosoina^ Planes^ Sterphiis^ Crepido- 

 tnyia (new genus), Philippiviyia (new genus), Tatuomyia (new 

 genus), and Emophora Philippi. 



Because of the great difference between the faunas of South 

 America and the rest of America, including the West Indies, the 

 faunas of the two regions have been treated separately. It is of in- 

 terest to note that in America the genera Xylota and Xylotomwrn, 

 {Xylota^ in part), as here understood, occur only in the Nearctic 

 region (several Mexican species occur at high altitudes) while other 

 genera Planes^ Crepidomyia^ Sterphas, presumably take their place 

 in tropical America. 



NORTH AMERICAN AND WEST INDIAN XYLOTINI 



The four additional genera, noted above. Planes Rondani (tropi- 

 cal), Xylotoinima^ new genus {Xylota, in part), Xylotodes, new 

 genus {Br achy palpus, in part), and Hadrmnyia Williston {Pocota, in 

 part) are recognized and included in the North American fauna on 

 the following grounds: Planes was made a synonym of Syntta by 

 Williston; but the type species and its congeners (all tropical) have 

 been assigned to Xylota and Syritta. It proves to be intermediate 

 between Xylota and Syritta but is a well-defined group. 



The characters here used to define the different groups of Xylo- 

 tini bring about the division of Xylota and Brachypalpus into two 

 genera each, Xylota and Xylotomima, Brachypalpus and Xylotodes, 

 respectively. These four groups are fully equivalent to the other 



