EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 113 
of the ground color. Sometimes the apex of the wing is pure white; sometimes 
the extreme tip has a few golden scales. There are thus six white spots (four 
of these are the extremities of fasciæ) along the dorsal margin and five on the 
costal margin, separated from one another by ground color. These correspond 
in position with the points of origin or with the tips of the nervures. The 
positions of the white spots with respect to the nervures are as follows: the 
white streak at the base extends somewhat obliquely, lying over the point of 
origin of the tubular part of the upper median vein; the first fascia lies proximally 
over the tip of vein 12, distally over the origin of the tubular part of the upper 
median vein; the second fascia on the dorsal margin lies over the tip of vein 1b; 
the pair of white spots at three-fourths lie over the tips of veins 10 and 2 respec- 
tively; the white fascia beyond, over 9 and 5; the last white fascia lies over vein 7 
on the costa. These white unpigmented areas are the interspaces between 
bands of ground color, seven in number, of which the first two are united on 
the costa. 
In L. oregonensis, the same number of white interspaces are present with 
the exception of the white spot at the base of the dorsum, but the fascie are 
more bent. The ground color is a deeper golden, and, whereas in tiliacella the 
fascie beyond vein 10 are represented by a few pale yellow scales only, the 
ground color is distinct, and the fourth fascia is black margined. "The extreme 
apex of the wing, which in tiliacella showed only a faint tinge of golden, contains 
a black apieal spot. In affinis, tritenianella (Fig. 5), ostensackenella (Fig. 7) 
and marieella (Fig. 8) there is a reduction in the number of white fasciæ 
and spots; the spots over veins 9 and 5 are wanting, and the ground color 
extends uninterruptedly from vein 10 to vein 7. In ostensackenella, the white 
streak enclosing the apex has become divided into a pair of opposite spots; the 
base of the wing is dark brown. In affinis and tritenianella, the white streak 
before the apex does not extend entirely aeross the wing. In tritenianella, the 
first white fascia is situated before the tip of vein 12. As it occupies the same 
position with respect to the origin of the upper median vein as the corresponding 
fascia in tiliacella (Fig. 7), it would seem that the origin of this vein is the 
factor determining the position of the first fascia. This conclusion is cor- 
roborated by identical observations on other species. 
Г. fragilella (Fig. З) and Г. celtifoliella (Fig. 4) are not closely related 
to the preceding members nor to one another. In both, the fasciæ are 
densely dusted internally with dark-tipped scales; in fragilella, the fasciz are 
suffused with pale yellow; in celtifoliella, the fascize are acutely angled, and the 
oblique costal and dorsal arms reach the margins proximal to their usual position. 
As will be seen later, this displacement of the extremities of the first two fasciæ 
proximally is of common occurrence and has been one of the principal forces in 
the evolution of the species of this genus. 
Desmodiella (Fig. 9), the single representative of the subgenus Porphy- 
rosela, which structurally is in advance of Lithocolletis, has retained the banded 
