EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 143 



racial development, renders it highly probable that there has also been a far- 

 reaching modification from the ancestral condition of the extent of the color 

 areas. These phylogenetic changes are scarcely or not at ah repeated in the 

 ontogeny. Three primitive bands are still preserved during the early stages 

 in the apex of the wing; the band proximal to these shows unmistakable signs 

 of its origin from a straight transverse band, its outer edge being straight. We 

 may, therefore, with reasonable certainty, conclude that the color pattern of 

 the basal part of the wing may be traced back through a series of phyletic changes 

 to its origin from the first three primitive bands. 



The ontogeny offers no direct testimony of the means by which these results 

 have been accomplished; it has given, however, visible evidence of two actual 

 dynamic methods by which changes have been wrought; namely, the middle 

 portion of each hand may he produced distally until it comes in contact with the 

 hand heyond it; the extremities of a hand may he hroadened hy heing produced proxi- 

 mally. Thus are produced, first, angulated fascise; second, slightly obhque 

 pairs of opposite streaks; the final effect of the second of the above processes, if 

 acting alone, is the entire obhteration of the white streaks. That a third process 

 has been at work is indicated by observations upon adult forms. The dorsal of 

 the first pair of white streaks in L. cratcegella (Fig. 36, PI. Ill) does not occupy its 

 primitive position over vein 16 but has been displaced toward the base, and vein 

 16 reaches the margin within Band IV; that is, there has been an extension of 

 the extremity of Band IV in this direction over the area formerly white. But 

 since a white streak still remains, there must have been a compensating drawing 

 away of the outer edge of Band III at its extremity. Such a withdrawal of 

 pigment cannot, of course, be observed ontogeneticahy. A third dynamic process 

 in the transformation may, therefore, be stated thus : the extremities of a hand may 

 he narrowed hy the retraction of pigment from their outer edges. This is an example 

 of the shrinking away of a band at one end. In this case, the shrinking takes 

 place at the outer edge of the band only. The result of the combined action of 

 the second and third of these processes is the progressive movement of the 

 end of the band toward the base. 



These three processes are sufficient to explain the origin of all the types of 

 marking in this genus; the specific results in any case are due to the manner and 

 extent of their action; that is, whether they act singly or together and to the relative 

 rapidity of action of the three processes. How they have combined to produce 

 these various types will be discussed in detail under the heading of phylogenetic 

 development. 



In the second division of the genus, the extent of the areas of ground color 

 undergoes very little change during development. The ground color appears 

 in the earhest stages over those areas which in the adult are occupied by yellow 

 or reddish yellow scales or by dark tipped yellow scales. The scales, which in 

 the adult are white with dark brown, gray or black tips, do not receive pigment 

 until much later; they then pass directly to gray or brownish gray and thence to 



