9-1 THE BUTTERFLIES OF THE WEST COAST 



b, Female, Summit, Cal., 1,500 feet altitude, June, 

 1S92: Author, 

 bb, Female, underside, Tallac Peak, 10,000 feet alti- 

 tude, July, 1S92 ; Author. 

 Flava is supposed to be a dimorphic female of Sis}"mbri, no 

 male having yet been foimd, and always yellowish in color, like 

 these figures. But it would not surprise me to know that there 

 is a male, and that it is a sort of a twin species to Sisymbri. It 

 seems to inhabit higher altitudes than Sis}-mbri by 2,500 to 3,000 

 feet, and to be absent at Sis}Tnbri"s lower ranges. 



No one has ever bred the larv^ae of Flava, nor is the lar^^al food- 

 plant known, though presimiably it is any one of the cruciferous 

 plants ; the egg, also, has never been described : it must, however, 

 be fertile, judging from analogy, for other dimorphic females are 

 always verj- prolific, tending to out-breed the normal-colored 

 females. 



37. Pieris Nelsoni. Xot elsewhere illustrated in accessible form. 



Plate \" ; Figure 37. 



Of Xelsoni only one male specimen has ever been taken; that 

 one by Mr. Xelson, at St. Michaels, Alaska. The figure here 

 shown is a photographic copy of a pen-drawing by Miss Colgan, 

 of the lithograph figure of Mr. Edwards, published in 1883, in his 

 Butterflies of North America, an expensive work, and inaccessible 

 to most people. 



The right-hand wings are the upperside, and the left-hand ones 

 are the underside. The pen-drawing is well done, as an error 

 which crept into the drawing made by the lithographer, as the 

 expert lepidopterist will perhaps notice, is faithfully copied. 



38. Pieris Occidentalis. 



Plate V : Figures 38, b. 



Fig. 38, Male, Ellensburg, Eastern Washington, :May. 1890; 

 Author. 

 b. Female, Sierra Nevadas, Cal., 7,000 feet altitude, 

 1892; Author. 

 Occidentalis is a ver}- common butterfly all over the whole west- 

 em part of the United States, west of the Rockj- Mountains ; being 

 rather a cold species, and loving the more northern parts bet- 

 ter than the southern. On the immediate Coast it is not seen much 



