EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 121 
ment ontogénétique, sont analogues aux phases que le dessin de l'espéce du 
Papillon a dû parcourir pendant son developpement phylogénétique, que le loi 
qui gouverne la biogenése est aussi confirmée par ce procédé, qui s'accomplit 
pendant la métamorphose de l'insecte, et qu'en fin les théories de Eimer sont 
solidement fondées, quand il dit que chaque animal ne peut varier que dans peu 
de directions determinées par les influences du dehors et par sa propre consti- 
tution, et que l'espèce se forme par génépistase.”’ 
Recapitulation is, however, only partial and confined to primitive forms: 
“Тез phénoménes de la phylogenése se produisent le plus clairement dans 
le developpement du dessin chez les formes les plus primitives. Chez les groupes 
les plus advances, ces phénoménes sont masqués par l'intervention dela tachy- 
genése qui montre sa plus grande influence dans le developpement des ailes 
inférieures." 
With regard to the succession of colors upon the wing, the same author 
finds that it is only in the primitive forms that the scales forming the dark mark- 
ings pass through the intermediate shades of yellow to reach their final gray or 
black condition; in the higher forms, they remain uncolored until the scales 
forming the ground color reach their full development, later passing directly 
from the colorless stage into gray or black. The color appears first at the tip 
of the scales, spreading gradually to the base. Scales which are destined to 
acquire their pigment later are not fully formed when the seales of the ground 
color attain the adult form and color. Therefore, color may be taken as a 
measure of the degree of development of a scale. 
2. Methods. 
In the study of the development of color in the wings of Lithocolletis, speci- 
mens of the summer generations were used for observation. No overwintering 
pup have been observed. In the summer generations, the average duration 
of the pupal state is about a week; it may be as short as four or five days. 
The chrysalids were removed from the mines shortly after pupation and 
kept under careful observation. For some time, no change in the brown color 
of the pupa is to be observed, then two faintly darker brown spots, corresponding 
in position with the eyes of the imago, become visible through the pupal envelope. 
These spots rapidly turn black, and very shortly after, the wings, which up to 
this time have appeared transparent through their thin chitinous envelope, 
begin to lose their transparency. This marks the beginning of the white stage. 
A day or two later, the yellow colors begin to appear upon the wing. The chief 
difficulty in the study lies in securing a suitable series of these earliest stages, 
as the colors are very faint at this period, and numerous dissections are often 
required before the necessary material ean be obtained. In later stages, the 
markings are visible through the pupal envelope, and a choice of specimens can 
be made with relative accuracy. 
The dissections were made in .6 per cent NaCl solution under a simple 
