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 hypothesis 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 

 facts 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 argentifimhriella (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 

 place 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. 



In all of the groups whose evolution has been traced, modification in the 

 shape of Bands II and III, 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 (cf. 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 



