EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 163 
spots which are situated near the edge of the wing is largely controlled by the 
wing-folds or creases.”’ 
Eimer has derived the various types of coloration from a series of transverse 
stripes (termed by him longitudinal because parallel to the longitudinal axis 
of the body) which break up into spots which fuse crosswise to form markings 
parallel to the longitudinal nervures, and finally fuse to a uniform color. New 
markings appear on the body of the animal from behind forwards and from above 
downwards, or conversely, whilst the old ones disappear in the same direction 
and succession. | 
I have shown that the ground color has been derived from a series of such 
transverse elements; conversion into a uniform color has taken place directly 
by an extension of color onto previously unpigmented areas, distad through the 
middle of the wing in the cell, proximad on the margins. The positions of the 
markings are arbitrarily determined. They are dependent upon the level at 
which evolution in the pattern of the ground color acting in a few definite direc- 
tions has come to a standstill. The actual appearance of the markings is prob- 
ably due to physiological activities whose nature is not understood. The first 
markings are usually transverse, rarely longitudinal when the modification 
in the ground color has been far-reaching. "These transverse markings are in 
the nature of narrow lines or streaks, phylogenetically the forerunners of the 
bands of higher Lepidoptera. Since the streaks and lines of dark scales in Litho- 
colletis still retain their primitive condition as originally laid down, it is not to be 
expected that the laws which Mayer has given, based upon the transformation of 
spots and bands in the higher Lepidoptera, would find wide application in this 
group. Portions of a pair of such streaks in Lithocolletis wil be found at the 
margins and in each interspace which the band from which they are derived 
crosses. Breaking up of bands formed by the growing together of these streaks 
will result in conditions such as Mayer has described for spots and series of spots. 
Any spot such as the apical spot is bilaterally symmetrical and occupies the 
center of its interspace. The primitive bands from which the ground color has 
been derived and which have been regarded as a primary set of markings upon 
which a second set, the markings proper, have been superimposed, have exhibited 
the tendency toward shrinking away at each end. 
The ultimate causes which determine the definitive positions of the primitive 
bands are unknown. Von Linden has found that in the lower orders of insects, 
the coloring matter has a tendency to collect on transverse veins; this however 
does not bring us any nearer to a real explanation of the phenomenon of colora- 
tion. The probability that the origin of the markings, which appear secondarily, 
may be traced directly to physiological factors, renders it reasonable that the 
appearance of the primary series is conditioned by like physiological and morpho- 
logical factors within the organism itself and is independent of external factors. 
Evolution in the pattern of the primitive series of bands has been shown to 
have taken place in a few definite directions; the diverse patterns which have 
