March, 1910.] OSBURN : STUDIES ON SyRPHID^E. 57 



offering such varietal differences." Verrall (1. c.) also suggests that 

 " Williston's var. arcnatns may well be Walker's 6". arcucinctus." 

 However, Mr. E. E. Austen, of the British Museum, has carefully 

 compared specimens for me with the type of arcucinctus and assures 

 me that Walker's arcucinctus is none other than arcuatiis, and that 

 he is unable to identify the present species with any other. The 

 " var. arcuatns " of Williston is, then, not Walker's arcucinctus 

 {^^ arcuatiis) , but a different and hitherto undescribed species, as I 

 believe the following characters are fully sufficient to justify: 



S. pcrplcxus. S. arcuatus. 



1. Third vein nearly straight, and i. Third vein strongly curved. 



correlated with minor dif- 

 ferences in venation. 



2. Pile of the pleurae white. 2. Pile of the pleurae yellowish. 



3. Two rounded separated spots 3. A single biarcuate black band 



above the antennae. above the antennae. 



4. The black of the cheeks and 4. The black of the cheeks and 



facial stripe shows little facial stripe usually fused on 



tendency to fuse. the oral margin, at least in 



American specimens. 



The first and third characters of the above list show no tendency 

 to intergradation, and all four apply equally as well to females as 

 to males. 



Description of Plate I. 



Fig. I. S. arcuatus. Head of male, front view. Note the biarcuate band 

 above the antenna! fossae. 



Fig. 2. Do., head of female, a rather melanistic specimen showing the 

 supra-antennal band connected with the black of the vertex. 



Fig. 3. Do., side view of head of female. 



Fig. 4. S. perplexus, head of male, front view. Note the pair of supra- 

 antennal spots extending down to the antennje. 



Fig. 5. S. perplexus, head of female, a rather melanistic specimen show- 

 ing the supra-antennal spots connected with the black of the vertex. 



Fig. 6. S. perplexus, sideview of head of female. 



Fig. 7. Wing of S. arcuatus. 



Fig. 8. Wing of S. perplexus. 



