184 



discal nervule to its uttermost extremity, forming, with the black 

 body, an elegantly formed T ; this band has a white streak in it at 

 the base ; beyond the costal band, and connected with it by the black 

 edge of the costal border, is a large apical spot, the inner edge of 

 which runs parallel to the outer edge of the extension of the costal 

 band, till it reaches the first inferior nervule, when it curves towards 

 the base a short way, and again extending downwards, with an in- 

 curved border, reaches the second inferior nervule, where it is rather 

 abruptly broken ; this spot has three or four, sometimes five white, 

 unequal, oval, sometimes round spots, the largest nearest the apex ; 

 some blackish scales follow the principal nervures of the secondaries 

 for a short distance, and the tips of the nervures are sometimes black, 

 otherwise there are no markings on the secondaries of the male, ex- 

 cept the dusky reflection of the markings of the lower surface, which 

 the transparency of the wing allows ; the female, however, repeats 

 slightly at the outer angle the markings of the lower surface. 



Beneath, pure white ; the markings of the upper surface of the 

 primaries are repeated, with the white spots and streaks slightly en- 

 larged and increased ; the nervm-es of the secondaries are all nar- 

 rowly bordered with blackish scales, which expand at the tips ; 

 commencing at the termination of the first superior nervule, a sub- 

 marginal narrow band approximately follows th^ curve of the margin, 

 is bent at the third superior nervule, and extends to the inner angle. 



Labial palpi with mingled black and white hairs ; antenna3 black, 

 with white scales scattered irregularly over the sides and under sur- 

 face, as far as the club. Body black, with whitish hairs, especially 

 below. The wings expand two inches. 



It represents in Washington Territory the P. Sisinibrii Boisd. of 

 California. A large number of specimens are in the Museum of 

 Comparative Zoology, obtained by Mr. A. Agassiz at the Gulf of 

 Georgia. 



The distinction I have made between males and females in the 

 foregoing descriptions, is founded upon characters which I first noticed 

 by comparing together the two sexes of P. protodice, a species whose 

 sexes have been known for a long time, and which are easily distin- 

 guished by their markings. On placing together, side by side, series 

 of males and females of this species, it was discovered that there was 

 a sexual distinction in the cut of the hind margin of the secondaries ; 

 it consists in the female having the outer angle more prominent, and 

 80 the whole hind margin less regularly curved, or, as it might be ex- 

 pressed, more flattened, — these difierences, though slight and requir- 

 ing a careful examination, hold persistently in all species of Pieris I 

 have examined. I have in several cases tested it carefully, by 

 separating, upon this characteristic, the specimens of those species 

 which exhibit two classes of individuals with distinct markings, and 



