24 Mr. C. H. T\ Townsend on Biptera 



species of Nausigaster occurring in North America, three of 

 "which Dr. Williston had before him when writing his 

 ' Synopsis of ISyrphidfe.' These are mentioned on pages 21- 

 22 under the wixmo, oi JSf. punctulata. Dr. Williston has been 

 loth to separate the forms as distinct, on the picture of the 

 wings alone ; but when material from several widely separated 

 localities shows a constant pattern for each locality, supple- 

 mented by differences in the thoracic vittas, I tliink they may 

 properly be separated and accepted as good species. In con- 

 nection with iV. meridionalis from the Hio Nautla, therefore, 

 I wish to present here the following notes on the separation 

 of the forms of Nausigaster^ although three of the species 

 concerned belong to the fauna of Texas, New Mexico, and 

 California. 



The single female from New Mexico, from which Williston's 

 description of punctulata was drawn, is the only specimen of 

 that species so far recorded. I have seen another from 

 Rincon, N.M., taken by Cockerell on flowers of Chilopsis 

 linearis (Cav.), DC, July 5, which agrees with Williston's 

 description in the wing picture. 



The five males from California, together with the additional 

 males and females from the same place (see Will., Synop.), 

 constitute another well-marked species, the specimens all 

 agreeing with each other. For this species I propose the 

 name unimacidata. It is distinguished by the single spot of 

 the wings and the five thoracic vittre. 



The male from the Isthmus of Tehuantepec forms a third 

 species, which I have considered to be the same as meridio- 

 nalis. It should be stated that I have not seen the Tehu- 

 antepec specimen nor the Brazilian specimens referred by 

 Williston to the same species, but that I refer them to 

 meridionalis on the statements of Williston regarding the 

 picture of the wings. 



A fourth species from Texas I describe below. These 

 four species may be separated as follows : — 



Tahle of Species of Nausigaster. 



1. A single spot on the wings ; five thoracic 



vittse unimaculata, sp. n. 



(California.) 

 Two spots on the wings, the spots not con- 

 fluent ; only two thoracic vittfe pimcfidaffi, Will. 



(Xew Mexico.) 

 The two wing-spots confluent, forming a more 

 or less well-defined and extensive picture ; 

 four thoracic vittse. (Lowlands of Texas to 

 Brazil.) 2. 



