EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 111 
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 
fascim, suggested the possibility that such a transversely banded arrangement 
of pigment areas, alternating with unpigmented fasciæ, 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, phylogenctically, 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 
that the primitive color pattern consists of a series of seven transverse bands, separated 
from one another by 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- 
tinetions, 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 indieate the early branching of this stem of the phylogenetie 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 specifie differences must be 
