146 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 



the phylogenetic 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 dynamic forces producing constant changes in the out- 

 Unes 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 hands superimposed upon an 

 earlier set, follows the same order for the ontogeny as for the phytogeny; 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 hand hecame fixed in the phytogeny. 



InL. 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 

 hand remains stationary, and hence a margin will develop here earlier than at the 

 extremities of the hand. 



In Cremastohomhycia ignota (Fig. 62, PI. IV), the development is very similar 



