140 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 



Cremastobombycia ignota F. and B. 



In the youngest specimen examined^ one in which the ground color was pale 



yellow^ the extent and position of all the adult markings (Fig. 62, PL IV) is defined 



{Fig. 2Jj) . The paleness is especially marked toward the apex, where it is difficult 



r,r to distinguish the markings at all. The white fascia 



III l^ V+J/I [77 . 



^^^^ is considerably broader than it will appear later. A 



careful examination shows it to be composed of two 

 parts, an inner fascia which is to form the white fas- 

 cia of the adult and in which the scales are whiter 



Fig. 24. Early stage in the de- ^j^^ ^^^ f^^y formed, and an outcr fascia, where the 



velopment of color in the wing of , ,1 n i i i i 



(7 ignota. scales are not as large nor as well developed and are 



somewhat buffish in color. These scales will later 

 form the black scales of the margin. This same thing is true of the other 

 streaks but is not as noticeable except in the case of the first costal because of 

 their more irregular shape. The band between the pair of streaks at three- 

 fourths of the wing length and the streak enclosing the apex is, as shown by its 

 position, equivalent to Band V + VI. The white streak before the apex is situ- 

 ated over the tip of vein 7. 



In a later specimen, the ground color has deepened to that of the adult. 

 The scales in the apex and in the cilia remain concolorous with the wing and are 

 not darker at their tips. The dark external margins of the white fascia and 

 streaks are appearing simultaneously, and all are equally advanced. The 

 scales forming them correspond in position with the colorless scales which formed 

 the outer part of the fascia in the preceding stage. The pigment, which is pale 

 gray without a tinge of yellow or brown, is evenly distributed throughout the 

 entire scale from the base to the tip. None of the internal margins has appeared. 



In a later stage, the external margins are black as in the adult, and internal 

 margins are present on the costal end of the first white streak and the fascia. 

 There are no internal margins on the pair of streaks at three-fourths. As 

 margins of these streaks are not always present in the imago, it is impossible to 

 determine conclusively whether they normally appear after the internal margins 

 of the fascia and the first streak. However, as will be shown later in the dis- 

 cussion, variable characters tend to appear later in the ontogeny than the fixed 

 characters of a species. 



The observations on the development of color in the wings of C. solidaginis 

 (Fig. 60, PI. IV) agree very closely with those on the preceding species. The 

 configuration of the color areas at their first appearance is the same as that of 

 the adult. In this species, however, the scales which are to form the dark 

 margins in the adult are pale yellow instead of, as in ignota, being colorless 

 and not fully formed. A comparison with the adult shows that these are 

 dark tipped yellow scales, the dark pigment being found at the tip of the scales 

 and not, as in ignota, almost uniformly distributed throughout the entire 

 scale. 



