146 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 
the phylogenetie development of this type of marking, therefore, it is possible 
that the margins appeared on Band IV while the basal half of the wing was still 
under the influence of dynamie forees producing constant changes in the out- 
lines of the areas of ground color. No margins could have appeared in the basal 
half of the wing until after these outlines had become permanent. Some of 
these changes, as has been already shown, are such as cannot be repeated during 
pupal development. Hence the color areas in the basal half of the wing tend 
to be laid down in their final shape. The sequence of the appearance of dark mark- 
ings, which are in reality a second series of transverse bands superimposed upon an 
earlier set, follows the same order for the ontogeny as for the phylogeny; that is, in 
this second and more recent set of characters, there is an actual recapitulation. The 
margins of Bands V and VI appear later, corresponding, therefore, to the sequence 
in the time of appearance of these bands phylogenetically, hypothetically based 
upon that of L. tiliacella. The margin on the upper side of the basal streak 
corresponds in time to the outer margins of the bands; it appears before inner 
margins develop. An outer margin of a band tends to appear first near the costa 
or dorsum, an inner margin near the middle of the wing; that is, at the apex of 
the outer side of a white streak, these being the parts of the edges of the bands 
which have reached their permanent position earliest. Therefore, the relative 
time of appearance of the dark margin of any band in the ontogeny is dependent 
upon the time when the edge of that band became fixed in the phylogeny. 
In Г. morrisella (Fig. 48, Pl. III), margins are formed almost simultaneously 
on either side of the white streaks by a direct change to gray and thence to black. 
The pigment in the other black scales develops in a similar manner without 
passing through the usual intermediate stages. The gray and black pigments 
make their first appearance at an early stage, while the ground color is still 
pale yellow. The structural differentiation of the white scales, the massing of 
black scales in the dorsal half of the wing, the exceedingly large apical spot and 
the black longitudinal streak in the fold all indicate the very high phylogenetic 
position of this species. Upon the addition of these newer characters, the earlier 
ones were crowded closer together and pushed farther back into the ontogeny, 
resulting in their contemporaneous development. 
In the species of the second division of the genus, dark margins develop in 
conformity with the principles already enunciated. There are certain minor 
differences between this and the preceding division attendant upon the original 
unexplained diversity in the inherent tendencies of the two divisions. The dark 
margin appears first on Band IV in the middle of its inner edge, in contrast to its 
appearance in the other division on the outer side and near each end of this band; 
the same is true for Band III. This is a necessary consequence of the action 
of the three general processes of evolution; the middle of the inner edge of any 
band remains stationary, and hence a margin will develop here earlier than at the 
extremities of the band. 
In Cremastobombycia ignota (Fig. 62, Pl. IV), the development is very similar 
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