132 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 
The darkening of scales in the cilia around the apex and just below it on 
the termen and the dark margins of the first costal and dorsal streaks are the 
next characters to appear. A wing examined at this stage shows the scales in 
the cilia brownish with scarcely a tinge of gray, the margin of the first dorsal 
streak somewhat paler and brownish yellow, extending from the cilia to vein 2, 
and the margin of the first costal streak pale and scarcely distinct. These 
observations are in agreement with those made on L. crategella and ostryefoliella; 
namely, that the dark markings appear earliest in the apex of the wing on Band 
VII and soon after on Band IV. 
The process of development consists now merely of the gradual appearance 
and darkening of the margins of the other streaks and the extension of the line 
in the cilia to the first dorsal streak. 
Lithocolletis morrisella Fitch. 
At a period when the entire wing, viewed by transmitted light, seems uni- 
formly colorless, the white markings as seen by reflected light are definitely laid 
down as they will appear in the adult (Fig. 48, Pl. III) and have already acquired 
the lustrous pearly tint characteristic of the adult. This white appearance is 
due entirely to the structural modification of the scales described earlier in this 
paper and cannot be in any way ascribed to a precocious development of the 
scales over these areas, since, when examined, all of the scales of the wing are 
seen to be fully vene 
With the first appearance of pigmentation, a bul yellow suffuses those 
portions of the wing only which are destined to be yellow in the adult (Fig. 16). 
In the basal half of the wing, therefore, the yellow is 
confined mainly to the region above the fold; there is, 
however, a faint yellow tinge just before the dorsal arm 
S of the fascia. There is a scarcely discernible tinge of 
Fic. 16. Early stage in gray at the base of the dorsum below the basal streak 
the development of color іп and before the first dorsal streak. At the tip of the wing, 
the wing of L. morrisella. 
over the area to be occupied by the apical dot, the scales 
are beginning to turn gray, those outermost being the deepest. Otherwise, the 
areas occupied by gray and black in the adult and by the white streaks appear 
by transmitted light uniform and colorless. Examination by reflected light 
shows that these two kinds of areas are not homologous, since the white streaks 
stand out clearly as structural modifications, while the scales margining them 
and those below the fold are duller and lack the pearly luster. The bands and 
the white fascia and streaks occupy their normal positions. The absence of a 
white streak over the apex of vein 7 is accounted for when it is seen that the 
apical spot has acquired such proportions as to cover the tip of vein 7, which in 
this and related species reaches the margin nearer to the apex than usual. 
In the next stage examined (Fig. 17), the ground color has deepened some- 
what, and decidedly more of the grayish tint has developed. The dorsal part 
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