124 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 



been preserved in its original primitive condition as seven distinct transverse 

 bands; fusions either partial or entire have taken place between two or more 

 adjacent bands. Displacements have also occurred^ due to a shrinking away 

 of color from one side of a white interspace and its extension over the white on 

 the other side. Finally^ some of the bands may have shrunk away almost 

 entirely. 



The following is a list of the species in which the development of the pattern 

 has been traced from the first appearance of color to the adult markings : 



Lithocolletis tiliacella Cham. 

 Lithocolletis tritcenianella Cham. 



Lithocolletis cratcegella Clem. 

 Lithocolletis ostrycefoliella Clem. 

 Lithocolletis lucidicostella Clem. 

 Lithocolletis morrisella Fitch 

 Lithocolletis hamadryadella Clem. 

 Lithocolletis hethunella Cham. 

 Lithocolletis ulmella Cham. 

 Lithocolletis cesculisella Cham. 

 Cremastobombycia ignota F. and B. 



Species in which two or more of the bands 

 have been preserved almost in their 

 primitive condition as respects position 

 and shape. 



Species in which changes in shape or 

 position or both and more or less com- 

 plete fusions of some of the bands have 

 taken place and certain differentiations 

 and specializations have appeared, such 

 as the development of black scales at 

 places other than those directly con- 

 tiguous to the white interspaces be- 

 tween the bands. 



In the following species, the development of the pattern was observed only 

 in part for the purpose of comparing the development of certain characters in 

 these species with that of similar characters in related species, or with a view of 

 determining the relative time of appearance of certain characters: 

 Lithocolletis hageni F. and B. 

 Lithocolletis robiniella Clem. 

 Lithocolletis carycefoliella Clem. 

 Cremastobombycia solidaginis F. and B. 



In all of the species studied, the wings are at first transparent and glassy 

 in appearance, corresponding to the period, as observed by Mayer (^96), before 

 the protoplasm has been retracted from the scales. Following this is the so- 

 called white stage, in which the wings appear by reflected light almost pure white 

 and by transmitted light pale bullish, due to the hsemolymph contained within 

 them. The scales are at this period colorless and transparent, containing only 

 air. The white stage lasts from one to two days, giving way to a pale yellow 

 over certain defined areas, as the hsemolymph enters the scales and the pigment 

 begins to form. This yellow color may be preserved throughout pupal develop- 

 ment almost as originally laid down, or it may go through a process of transfor- 

 mation before reaching the adult condition. In either event, it gradually deepens 

 in tint and constitutes the ground color upon which the dark streaks (margins) 



