OF WASHINGTON, VOLUME XVII, 19 13 111 



both sexes; palpi rufous; front usually still more prominent than in 

 preceding. . . .Ennyomma clistoides subsp. sierricola new subspecies 



11. No strong median marginal macrochsetae on second segment in cither 



sex; hind crossvein of male in middle between small crossvein and 

 bend of fourth vein, that of female a little nearer bend; hairs of 

 parafacials outside marginal row normally vestigial, and marginal 

 row weakly developed; third and fourth abdominal segments with 

 marginal row of equally strong macrochaetse. 



Phasioclista m< tnlli i // 



Strong median marginal pair on second segment in both sexes; hind 

 crossvein much nearer bend of fourth in both sexes 12 



12. Hairs of parafacials normally well developed, especially marginal 



row; marginal row of macrocha?tse of third segment often not of equal 

 strength, due to partial development of extra bristles; face, third 



antennal joint and palpi except tips black Myiophasia setigera 



Bristles and hairs less developed on parafacials and abdomen; antenna 1 , 

 palpi and face wholly rufous. 



Myiophasia setigera subsp. oregonensis new subspecies 



It is highly important to separate and recognize the above forms 

 by reason of their value in geographic ecology. Those who lump 

 them ignore their true significance and are blind to the import 

 of ecologic and evolutional principles. The impress of the en- 

 vironment is upon each of them. When, in the course of time, 

 a series of some thousands of specimens shall have been secured, 

 representing all the forms of this group occurring in the princi- 

 pal ecologic centers of North America, the variation in the environ- 

 mental stamp exhibited by the series will furnish us a most in- 

 structive lesson in muscoid ecology. As large series as possible 

 should be gathered from every variety of habitat. Such plastic 

 forms as the present, by virtue of the very conditions which 

 make them so difficult to classify, are of far greater biologic 

 importance than those which show little change over wide ranges 

 of territory or throughout continental areas. It therefore goes 

 without saying that we should miss the kernel of biological investi- 

 gation, and secure only the chaff, were we to yield to the easier 

 alternative of lumping them. 



The following is the distribution of the 164 specimens studied. 

 to which are added published records of material not in the 

 U. S. National Museum collection, with character of biogeo- 

 graphic environment for each form: 



ENVIRONMENTAL AND GEOGRAPHICAL DISTRIBUTION. 



Myiophasia setigera 2 males, Brulah (8,000 ft.) and Pecos, 

 New Mexico (Cockerell); 2 females, Rociada and Santa Fe, 



