8 PBOCEEDINGS OF THE NATIONAL MUSEUM, vol.63. 



Chroysomasicera Townsend, Journ. N. Y. EInt. Soc, vol. 23, 1915, p. 230. 



Type designated, borealis, new species. 

 Chrysoexorista Townsend, Proc. U. S. Nat. Mus., vol. 49, 1915, p. 435. 



Type designated, viridis, new species. 



The type species of all the above genera have been examined, and 

 protracted effort has been given to the task of finding satisfactory 

 generic characters to separate them, but with little success. Realiz- 

 ing that several of them have been regarded by the later authorities 

 of Europe as valid for that continent, we have earnestly endeavored 

 to retain such, especially Phryxe and Carcelia. It seems to us, how- 

 ever, that the external characters show such complete gradation in 

 North American species that we can not discover natural lines of 

 division of more than subgeneric rank, as indicated in our table of 

 genera. Generic characters should be those of more ancient origin, 

 externally recognizable, and should exist in both sexes, although 

 they be supplemented by others which do not meet these requirements. 

 "Wliether a species lays large or small eggs we can not consider of 

 generic importance, as the complex reproductive modifications which 

 are so striking in the great Tachinid group seem to us of very recent 

 development here, and not correlated with any distinct characters in 

 other parts. 



We are dealing here with the immense central mass of the family, 

 in which large genera may naturally be expected. There is a wealth 

 of specific characters. A policy of splitting which would logically 

 terminate in a genus for every species is in the end ruinous to the 

 taxonomic scheme, as it eliminates the genus as a category and neces- 

 sitates the recognition of some substitute, as the supergenus or the 

 tribe. This might not be a serious matter if the genus were not by 

 convention a part of the scientific name, for which we can not substi- 

 tute anything else. 



The species known to Coquillett at the time of his Revision in 1897 

 were placed by him in Exorista. This genus had but one species 

 when erected, Musca larvarwn Linnaeus, which thus must be the type 

 of the genus, and which Coquillett placed in his Tachina. The type 

 of Tachina is Musca grossa Linnaeus, a widely different species, which 

 is also the type of the later genus E chinomyia. Tachina therefore 

 should replace Echinomyia^ Exorista should replace Tachina in 

 Coquillett's sense, and another name be selected for what Coquillett 

 called Exorista. For this last vacancy we select ZenilUa Robineau- 

 Desvoidy, which has not only as early a date as any in our list of 

 synonyms, but has page precedence over Phryxe^ Carcelia^ and 

 Aplomyia^ of the same date. Coquillett himself proposed these 

 changes for Tachina and Exorista in his Type-Species paper of 1910. 



Our grouping is considerably modified from that of Coquillett, 

 Revision, 1897, since, as will appear from the appended list, we have 



