3T7 



19. Gray. Spot contiguous to base of cleft mcdius 



White, coarsely irrorate with gray. Spot conspicuous, sliglitly before 

 base of cleft liniis 



20. Fringes in cleft of primaries dark some arion 



Fringes not dark ; in general about same shade as wing, with light and 

 dark areas fishii 



21. Primaries pure white with variably extensive dark marks, cloudy with 



exception of oblique patch. Median tibial tuft very slight brucei 



With strong median tuft on mid tibiae or not pure white 22 



22. Dorsal surface of abdomen with slightly diverging light and dark 

 streaks. Primaries with subcostal pale line, usually conspicuous, reach- 

 ing costa on each side of dark costal dot over base of cleft austcr 



Not such species 23 



23. Ground color of primaries even yellowish white or whitish with black 

 marks, pattern simple. Secondaries contrastingly dark. Western species 24 

 Ground color never tinged with yellow, sometimes more or less cream 

 colored or tawny but rarely whitish. Secondaries not conspicuously 

 darker 25 



24. Fringes in cleft of primaries very dark. Mid tibiae with median tuft 



castor 



Fringes of cleft pale. No tuft /"oZ/kx 



25. Slender winged gray insects. Primaries finely powdered with brownish 

 black and white. Inner margin usually with an underlying brown shade 



of variable extent grisescens 



Primaries blackish brown or blackish, conspicuously streaked with pure 



white 26 



Primaries creamy white to tawny brown with brown marks, if any. 

 Never extensively irrorate with blackish scales, and with little or no 



white 27 



Not such species 29 



26. Smaller, expanse rarely as great as 25 mm. Front of thorax and basal 

 half of patagia white, this shade definitely limited behind. Palpi gray- 

 brown above mcyricki 



Larger, rarely as small as 25 mm. White on thorax and patagia more 

 extensive and less definitely limited. Palpi mostly white iiihar 



27. With a brown streak in apex of second lobe of primaries, extending 



through fringe 28 



Without such a streak some occidentalis 



28. Thorax and patagia pale citrites 



Thorax and patagia pale in front only, this area sharply limited fieldi 



29. Fringes on inner margin of primaries neither white nor with conspicu- 

 ous clusters of white scales, sometimes with a very faint cluster and 



pencil of pale or whitish hairs 30 



These fringes sometimes almost white, always with one or more evi- 

 dent clusters of white hairs 33 



