——— ——— V 
| 
| 
| 
[ 
ТТТ ааа ق‎ 
EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 145 
The diseussion heretofore has dealt chiefly with the processes which effect 
the final limitation and configuration of the ground color. The general tendency 
toward the production of dark pigment in rows of scales adjacent to unpigmented 
areas has also been noted. These streaks of dark scales, which are usually 
transverse, and the various other characteristics, such as the apical spot, the 
longitudinal streak of black scales in the apex and the black streak in the fold, 
properly constitute the markings, in distinction to the ground color, and are 
superimposed upon it. While the progressive change in the configuration of 
the ground color is the important factor in determining the general evolution of 
the genus and the different stages at which development has halted form the 
starting points for the differentiation of the different groups of species, the develop- 
ment of the markings is the important faetor in determining the phylogenetie 
sequence of the individual species within each group. A knowledge of their 
mode of origin and relative time of appearance is therefore essential. 
In Г. tiliacella and tritenianella, it was seen that the dark margin develops 
first along the edge of Band IV, which is the first band to reach its adult shape. 
In L. tiliacella, the outer edge of this band has become fixed before all of the bands 
have even been laid down. The dark margin appears toward the costa and 
dorsum, in places where the outer edges of the band have undergone no change 
whatever since the first appearance of color. The dorsal margin seems to be 
in advance of the costal. There is no darkening of pigment along the bands in 
the apex, which appear comparatively late. From these observations, it appears 
that in the ontogeny, the dark margin develops earliest along the edge of that band 
which first reaches its definitive adult condition. Before dark margins can develop, 
the edge of a band must have remained fixed for an appreciable period of time. 
In L. crategella, ostryefoliella and lucidicostella, the dark margin on Band 
IV is also the first to appear. The apparent contradiction to the principle just 
laid down that a dark margin develops earliest along the edge of the band that 
has first reached its definitive adult condition, lies in the fact that in these species 
the color areas in the basal half of the wing are at the outset defined almost as 
in the adult, while the bands in the apex repeat the racial development. It 
might be expected, then, that the margin would appear earliest along the first 
pair of streaks. It has, however, required a much longer time in the evolution 
of the species for the basal half of the wing than for the apical half of the wing 
to acquire its present aspect; the development in the apical half has come to a 
standstill comparatively early in the phylogenetic history of the species. The 
observed recapitulation in the apical three or four bands during the ontogenetic 
development of the steps in the racial differentiation of the species is in harmony 
with the conclusions of other investigators that it is only among primitive forms 
that anything approaching a complete repetition of phylogenetic changes is to 
be found in the ontogeny. 
The apex of the wing (in respect to the conservation of primitive color 
areas) may be regarded as primitive in comparison to the base of the wing. In 
