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 fasciae) 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 obhquely, 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 16; 

 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 Hes 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 fasciae are 

 more bent. The ground color is a deeper golden, and, whereas in tiliacella the 

 fasciae 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 apical spot. In affinis, tritcenianella (Fig. 5), ostensackenella (Fig. 7) 

 and mariceella (Fig. 8) there is a reduction in the number of white fasciae 

 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 tritcenianella, the white streak 

 before the apex does not extend entirely across the wing. In tritcenianella, 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. 



L. fragilella (Fig. 3) and L. celtifoliella (Fig. 4) are not closely related 

 to the preceding members nor to one another. In both, the fasciae are 

 densely dusted internally with dark-tipped scales; in fragilella, the fasciae are 

 suffused with pale yellow; in celtifoliella, the fasciae 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 fasciae 

 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 



