An Unnamed Butterfly From 
San Francisco 
BY FORDYCE GRINNELL, JR. 
Rusticus acmon cottlei, new sub-species. 
8 expands 26mm. ¢ 26-30 mm. 
2, forewings, upperside. An intense purplish-blue, clearly de- 
fined in most specimens; a black discal spot; a broad, black border 
averaging 2.5 mm. in width, wider on the costal margin, clearly 
defined and not merging into the ground color in most specimens, 
in others this black border merges into the ground color between the 
apex and discal spot. Fringes white, and inside a distinct black line. 
Hind-wings, upperside: Purplish-blue, with usual red marginal bor- 
der, wide, and of an intense color, the enclosed series of black dots 
comparatively small. Underside: General ground color dark ashy, 
with the usual markings very well defined. 
é, upperside: Brilliant violet-blue, with the usual black border 
and white fringe; hind-wings, with a light-reddish border, very 
much reduced in size and intensity of color from the usual form of 
acmon. Undersides: Dark ashy, with the usual markings well 
defined. 
Habitat: Baker’s Beach, north of the Cliff House, within the 
city and county of San Francisco; collected during March, 1915, by 
Mr. James E. Cottle of that city. Types 1¢, 19, inthe collection 
of the author. 
This geographical race, restricted to Baker’s Beach, San Fran- 
cisco, can be compared with the spring form of acmon from other 
parts of California, and even from the opposite side of San Fran- 
cisco bay at Niles Canon, to which it is somewhat closely related. 
It can be distinguished, however, especially with the females, by the 
intensity, sharpness and distinctness of the deep purplish blue, the 
heavy black border; the greatly extended deep red border of the 
hind-wings; and darker ashy gray and distinct markings of the un- 
dersides. 
It is in the same category as the other blue butterflies of the San 
Francisco region: Xerxes, pheres, mertila, antiacis and behrii, which 
