a. — Costal region of the primaries shows as a clear 

 creaiB}^ white streaky concolorous with or but 

 slightly lighter than the collar, (ampulla of 

 clasper membraneos) vilifrons 



b. — Not so, — costal region never a white streak, 

 a^. — Head and collar concolously dark, brown or 

 brownish, contrasting with the ground color 

 of the primaries and thorax, (ampulla of 

 clasper chitenous) Brunneicollis 



b^. — Not so, — head and collar if concolorously 

 dark not contrasting with the ground color 

 of the primaries and thorax, 



a". — Wing-form short, stubby, trigonate (all ex- 

 cept from the far Northwest with male an- 

 tennal segments ciliated with blocks of long 

 cilia, presenting under a lens a sublamellate 

 appearance) (ampulla of clasper membrane- 

 ous) Trigona 



b^. — Wing-form not trigonate, 



a^. — Primaries with a blueish underlay' of smaller 

 scales ; transverse maculation usually visible 

 and scaled with same color, (containing two 

 species, — variata, the largest in the genus, 

 and scopeops, one of the smaller forms. 

 Only scopeops liable to confusion, with a 

 form of "placida." It only occurs in B. C, 

 Wash., Ore., and N. Calif., always with the 

 orbicular round; not large, and outlined by 

 a clean line) (ampulla of clasper mem- 

 braneous J^ariata 



b^. — Not so, — seldom with a blueish tint to the 

 primaries ; if blue scaling be present it is re- 

 stricted to the terminal area of the jjrimar- 

 ies (except in the placida form mentioned 

 above, 



a*. — Size large, wings broad, primaries square- 

 cut, 



a^ — S.t. line two toothed, lower tooth subdivided 

 into W-mark; (ordinary spots easily visible, 

 clearly outlined; orbicular large, oblique, 

 often somewhat flattened) (ampulla of 

 clasper membraneous) Alernata 



b^ — S.t. line without the W-mark; (orbicular 

 round or sub-round; only in aberrant speci- 

 mens oblique, sometimes absent), 

 83 



