EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 155 
ment of dark pigment. The result is a tendency toward a uniform distribution 
of ground color over the entire wing. 
It may be objected that the color pattern of the three species just discussed 
could have been derived directly and in a more simple manner from that of 
L. argentinotella (Fig. 11) by the broadening of the extremities of Bands 
II and III toward the base, resulting in the obliteration of the white streaks 
separating Band I from II and Band II from III. On this hvpothesis the 
greater changes have occurred in the middle of the wing since the oblique pair 
of streaks in the middle of the wing have been produced by the combined action 
of the second and third processes of evolution. "This is not in agreement with the 
faets observed up to this stage in the evolution of the color pattern, namely, 
that the greatest changes have occurred near the base of the wing, nor with the 
general principle that development is more rapid in the more proximal parts 
of an organism. 
2. The shrinking away of the ground color at the extremities of the bands 
may continue and the outer edges of Band III may be involved to a greater 
extent than hitherto observed. In albanotella (Fig. 42) evolution in this 
direction has ceased comparatively early, the darker ground color and heavier 
dark margins indicating the longer time occupied in specific differentiation. 
In argentifimbriella (Fig. 43) the withdrawal of color from the base of 
the wing has been almost complete and there has been no later extension of 
color toward the base from Band IV. In lucidicostella (Fig. 44) there is a 
slight extension of color along the dorsal margin; the halting in development has 
been too recent for a dark line of scales to develop on the streak of ground color 
extending along the upper side of the cell. In clemensella (Fig. 45) this 
streak has also disappeared. In the four preceding species, evolution has taken 
plaee more rapidly on the dorsal than on the costal margin of the wing. In 
quercialbella (Fig. 46) and trinotella (Fig. 47) the costal half of Band III 
has also shrunk away; the only transverse bands then remaining are the 
four apical ones. In the European fauna, the final consummation of this process 
is witnessed in such species as L. cramerella and L. tenella. Development has 
halted at different levels, as in our species, and dark streaks have appeared at 
the edges of the bands. Gradually then bands more and more distal have 
shrunk away, leaving behind them the dark fuscous streaks on an almost white 
ground. j 
In all of the groups whose evolution has been traced, modification in the 
shape of Bands II and ITI, in the early phases of evolution has progressed in the 
same direction and at approximately equal rates, so that the bands are of 
similar shape (сЁ. argentinotella, Fig. 11). 
In the following species evolution has proceeded independently in each of 
these bands. 
Changes may proceed very slowly on the inner edge of Band IV and outer 
edge of Band III; the tendency is then toward the preservation of a median 
