148 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 
margin; in L. caryefoliella, the dark margin of the fascia is complete before any 
pigment has developed in the area beyond it. In the imago, the patch of dusting 
beyond the fascia is an established constant character in bethunella; in caryafo- 
hella, the amount of such dusting is very variable, indicating its recent appearance 
in the species. 
It would seem then that only those characters permanently established and of 
long standing in a species exhibit this precocity of development; recently acquired or 
variable characters appear ontogenetically in the order of their phylogenetic sequence. 
This conclusion is confirmed by observations upon the mode of development 
ontogenetieally of other analogous dark markings. Comparison of imagoes 
indicates that the apical spot and the black patch in the apex have originated 
phylogenetically earlier than the streak of brown scales along the middle of 
the wing but later than the dark internal margins of the white fascize and streaks. 
In L. crategella, the pigment in the scales of the black patch before the apex, 
which is unquestionably a characteristic only acquired through differentiation 
extending over a long period of time, appears earlier than that in the brown 
scales extending along the middle of the wing and reaches its definitive adult 
condition while the latter are still wholly unpigmented. In L. hageni also, the 
apical spot appears sooner than the dark scales in the middle of the wing beyond 
the tip of the first dorsal streak. 
Such specializations as these cannot, however, have originated very early 
in the evolution of a species, and the observed phenomenon of their unduly 
precocious appearance and rapid development in the ontogeny requires additional 
explanation. In L. crategella, ostryefoliella, lucidicostella, hageni and morrisella, 
these were the first dark markings to appear. The first tinge of gray appeared 
before the ground color itself had reached its adult shade or rarely even before 
it had reached its adult configuration. It is possible that physiological causes 
act directly toward this end. In the racial development, the segregation of 
black scales over a limited area and the later modification of these scales structur- 
ally has been accomplished gradually; the results have become permanent in 
the species, and the scales, when first formed before any pigment has entered 
them, have a structure identical with that acquired late in phylogenetic develop- 
ment. It is suggested, in explanation of the phenomenon of the early appearance 
of black pigment in them, that the concentration of pigment-forming substances 
within a smaller space—the interior of these smaller scales—results in a more 
intense chemical action over a localized area and thus hastens development. 
The general conclusions which have been drawn from the study of pupal 
development may be summarized as follows: 
1. The primitive type of color pattern consists of a series of seven trans- 
verse bands, which, except the first, cross the wing perpendicular to the costal 
margin and are not wider than the unpigmented fascie between them. Their 
positions are determined by the course of the longitudinal nervures. 
2. In the evolution of the genus, changes in extent alone of bands are 
