EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 141 
4. Discussion and Conclusions. 
In general, I have found that the action of three processes is sufficient to 
explain the transformation of the seven primitive bands into the several existing 
patterns of the ground color. These three processes may be stated thus: (a) The 
middle portion of a band may be produced distally until it comes in contact with 
the band beyond it. (b) The extremities of a band may be broadened by being 
produced proximally. (c) The extremities of a band may be narrowed by the 
retraction of pigment from their outer edges. These three processes may act 
separately or in combination; the particular pattern produced is the resultant 
of their combined activity. The first two of these laws are based chiefly upon 
the changes observed during pupal development, the third law is deduced 
from adult characters, since the changes are such as cannot be observed directly. 
The evidence in detail is as follows: 
In L. tiliacella (Fig. 7), seven distinct transverse bands of ground color 
are laid down; of these, those numbered II, III and IV appear first; following 
these, Band I, at the base of the wing, appears continuous in the costal half of 
the wing with II; it is, however, sufficiently separated from it by the difference 
in time of appearance. The three bands in the apex of the wing appear last and 
undergo no change; the connection of Band V with IV is brought about entirely 
by the extension outwardly of IV along the middle of the wing. The changes 
in Bands II and III are brought about by the spreading of the color onto areas 
formerly unpigmented; that is, the fascia between II and III is narrowed by 
the very slight growth distally of II along the middle of the wing, its extremities 
remaining fixed, and by the extension proximally of III, chiefly along the margins. 
Band IV reaches its adult configuration earliest; it is also the earliest to acquire 
the black pigment on its outer edge. This does not appear in the middle of the 
wing, where the band has extended outwardly uniting with V. The outer 
edges of the extremities of Band III have remained constant in position, and the 
dark scales appear first here. In Band II, there has been the least change in 
shape; the deepening of the pigment along its outer edge occurs more uniformly. 
From this, it follows that while the general tendency is for dark pigment to develop 
along the outer edges of bands adjacent to unpigmented areas, the precise time of its 
appearance along any band or portion of a band in relation to other bands or portions 
of the same band is determined by the time when such bands or portions of bands 
reach their adult shape and color. The outer edge of a band in direct contact with 
another band acquires no dark pigment. 16 would appear from the observations 
on this species that the bands in their primitive condition are narrower than they 
are in the adult. A fascia may be narrowed by the uniform spreading of a band 
toward the base. 
These conclusions are corroborated by the observations on L. tritenianella 
(Fig. 5, Pl. IIT); all the bands, however, appear simultaneously, and at this time 
all are straight. There is, however, a reduction in the apparent number of bands, 
V and VI being completely united. Band IV seems no further advanced than 
