EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 127 



is present in the adult; that is, Band IV has not yet begun to extend outwardly 

 through the cell. The space separating V + VI from VII is at this stage about 

 one-half the width of V + VI and extends entirely across the wing, thus differing 

 strikingly from the condition found in the adult. 



The development for some time consists merely in a uniform darkening of 

 the ground color as first laid down without any change in the extent of the bands. 

 At a somewhat later stage, simultaneously with the darkening of the ground 

 color into the adult shade, changes in shape and more complete fusions of some 

 of the bands occur. As soon as the adult color has been attained, the dark mar- 

 gins begin to develop. A specimen examined at this period shows that while 

 no change has taken place in the form or extent of Bands I + II and III, Band 

 IV has become outwardly angulated as in the adult, thus narrowing, especially 

 in the middle of the wing, the white fascia separating it from V + VI. On the 

 dorsal margin. Bands V, VI and VII are completely fused, the small white costal 

 streak before the apex alone remaining to mark the position of the white fascia 

 between V + VI and VII. The scales along the outer edges of Bands II and 

 III are beginning to show faintly brownish tips, this color being about evenly 

 distributed along the entire edge of Band II; in Band III, the color extends 

 farther toward the bases of the scales in the middle of the wing. The scales of 

 the dorsal half of the outer edge of Band IV are dark reddish brown, almost as 

 in the adult, but on the costal half of the wing, there is only a very slight deepen- 

 ing of the yellow color, the margin here being considerably paler than the margins 

 of Bands II and III. There is a very slight deepening of scales on the outer 

 border of Band V + VI, adjacent to the white streak before the apex. The 

 dusting in the apex is dense, the color being darker and more blackish than the 

 outer margin of Band IV, and extends from the white streak well around the 

 apex and along the dorsal margin almost to vein 5. This dusting is considerably 

 greater in extent even in this stage than that of the overwintering forms in any 

 stage. 



Lithocolletis crataegella Clem. 



This species belongs to that large group in which the imago is characterized 

 by the presence of pairs of opposite white costal and dorsal streaks; that is, all 

 of the original primitive bands have fused at least along the middle of the wing. 

 L. cratcegella (Fig. 36, PI. Ill) possesses in addition a margined basal streak, ex- 

 ternal as well as internal margins to the white streaks (i. e., the dark scales 

 developed on both sides of the primitive bands and not only on the outer side, as 

 in the two preceding species), a streak of dark scales along the middle of the 

 wing, a patch of black scales in the apex and the blue iridescence of the scales in 

 the cilia. The study of the development of the wings in this form should there- 

 fore throw light upon the origin and mode of development of the above characters 

 and indicate their relative time of appearance. 



In the earliest stage examined (Fig. 12), at a period when the markings are 



