136 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 
is, however, prolonged outwardly at its angle along the wing to a position between 
the third pair of streaks. A comparison with the adult shows that the pro- 
longation of the fascia is oceupied by dusting on a whitish ground; that is, these 
white seales are destined to become black tipped. 
The third pair of streaks are situated normally over 
veins 10 and 2 respectively. "There is no white spot 
= over the tip of vein 9 on the costa. Bands V and VI 
Fic. 20. Early stage in the have fused. A quadrate area in the apex remains 
development of color in the wing colorless; the portion directly over vein 7 corre- 
of L. bethunella. в à 
sponds to the white streak normally situated here, 
the remainder will be occupied by dark dusting in thé adult. The scales 
around the margin at the apex are yellow; these in the adult will be brown 
tipped yellow scales. 
In a wing at a somewhat later stage, there has been some deepening of the 
ground color. There is a small patch of scales just beyond vein 7 which are 
brown tipped and darker than any other scales on the wing. In the extreme 
apex, the scales extending over the cilia are not noticeably dark tipped. Dorsal 
to the dark patch of scales, the scales over the formerly colorless area become 
gradually paler, until near vein 5 their tips show just a faint tinge of gray. АП 
the scales in the prolonged portion of the fascia are becoming pale gray tipped. 
There is also a faint gray tinge to the scales just below the tip of the dorsal 
arm of the fascia, continuous with the gray in the prolonged portion of the fascia. 
All of these scales are much paler than those in the apex just beyond vein 7 but 
approach in color those near vein 5. 
The margins of the remaining streaks soon make their appearance; the 
dusting of the apex reaches the adult condition earliest. 
A contrast in the sequence of development of dark marks is afforded by 
L. caryefoliella Clem. In this species, the margins of the first and second fasciz 
develop eontemporaneously with a small patch of dusting at the extreme apex, 
and the margin of the second fascia is entirely complete, though not as dark as 
in the adult, at a stage when there is no indieation of dark dusting beyond its 
angle. This dusting is very variable even in the adult, sometimes being very 
slight. The significance of the difference in development will be discussed later. 
I+ II ns Г Y" a il 
Lithocolletis ulmella Cham. 
In this species, the pale yellow color appears simultaneously over all those 
areas which are to remain yellow in the adult (Fig. 95, Pl. IV) or in which the 
scales are yellow with brown or blackish tips. The white streaks and the white 
dusted portions of the wing remain colorless. "Thus, the second costal streak is 
produced for a short distance along the cell, and the wing from vein 7 to the 
apex is colorless, but the scales around the apex and below the oblique dorsal 
streak, which are yellow with brown tips in the adult, have already acquired the 
pale yellow color. 
MM TEES rene ITE IIS INS a) ee RR ER, PR. MESE TAE ERST T RA 
