EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. Ill 



color pattern of the genus^ or an approach to it^ still exists among the modern 

 species. The presence, in several species, of a number of almost straight or 

 slightly modified transverse bands, separated from one another by unpigmented 

 fascise, suggested the possibility that such a transversely banded arrangement 

 of pigment areas, alternating with unpigmented fascise, was the primitive color 

 pattern of the genus. This idea received some support from the fact that in 

 L. tiliacella, whose pattern will be described in detail below, the bands in the 

 apex of the wing are uniformly pale yellow, with no trace of darker scales. Bear- 

 ing in mind the generally accepted fact that, phylogenetically, pale yellow is 

 one of the oldest pigmental colors, some portions of the wing of L. tiliacella are 

 probably still in the ancestral condition. In this species, seven distinct color 

 areas can be made out, most of which are completely separated from one another 

 by white (unpigmented) areas which lie over the origins or the tips of the nervures. 

 As no species has been found to have a greater number of separate pigmented 

 areas, and most of those which do not show a banded type of marking have 

 fewer such areas, the conclusion was reached from the study of the adult markings 

 thsit the primitive color pattern consists of a series of seven transverse bands, separated 

 from one another hy unpigmented areas. 



The verification of this conclusion rests upon the studies of pupal develop- 

 ment of the color pattern, which have also shown how the modifications in the 

 color pattern, characterizing the different groups described below, have been 

 brought about. 



The evidence for the above conclusion as to the primitive color pattern, in 

 so far as it is based upon adult characters, is given below. In this relatively 

 brief survey of the adult markings of the numerous species comprising the genus 

 Lithocolletis and its subgenera, the writer has been guided in the grouping of the 

 species, as far as practicable at this stage of the presentation of the results of the 

 research, by affinities determined through the discovery of the action of certain 

 definite laws in bringing about changes in the shape and extent of the color 

 areas. Occasionally, it has been found convenient to bring in arbitrary dis- 

 tinctions, used to separate the species systematically. This is true in the second 

 group of species discussed; here the presence of a median fascia, while doubtless 

 a character valuable to the taxonomist, is in no way an indication that the species 

 are closely related to one another. Evolution has proceeded along the same 

 line in the different species in respect to this one characteristic alone; the differ- 

 entiation of the other markings has been brought about in such different ways 

 as to indicate the early branching of this stem of the phylogenetic tree. 



In the discussion of the individual species, the characters referred to are 

 those developed through the action of general evolutionary tendencies. The 

 various levels which such development has reached before coming to a standstill, 

 mark the points where the different subgroups of species diverge from the main 

 stems. Within these subgroups, there have been numerous differentiations, 

 producing the actual species we now know. Such specific differences must be 



