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EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 151 
division of the genus does not in any way indicate that this is primitive; it has 
rather been produced independently in the two groups, by the action of the 
same three fundamental factors. 
The phylogenetie tree thus shows two main stems extending in different 
directions from a common origin. By the application of the three general 
principles directing the evolution of the pattern of the ground color, it is possible 
3 
Forphy | Wrphyrosela b 
: | Е 
; А ; 3 Flat. larval 
Lithocolletis Flat larval есейе Ё Tuy 
Jepiced Group Li dig 5 
y -Cremasiobombycia К 
О.) frm Оло) Form 
Fic. 25. Phylogenetic tree showing structural rela- Fia. 26. Phylogenetic tree showing relative time of 
tionships of the groups of Lithocolletis. origin of the groups of Lithocolletis. 
to retrace the steps in the origin of the different groups of species. "The evo- 
lution of the species of the “cylindrical-larval group," which will be discussed 
first, is illustrated on Plate III. 
In all of the species except bataviella (Fig. 58), there has been a fusion 
of Bands I and II along the costa. 
If evolution in the shape of Bands II and III has been in the same direction 
and at the same rate, and the outward growth of the middle of each has not 
been sufficient to bring it in contact with the band following, and this outward 
growth has been compensated for by an equal growth toward the base of the 
extremities of Bands III and IV, species characterized by two entire fasciz will 
be produced, the first at the basal fourth, the second at the middle of the wing. 
Where evolution ceases early, all or most of the bands may be preserved as 
transverse bands.  L. tiliacella (Fig. 1) has been differentiated as a species 
when, except for the fusion of I and II on the costa, Band IV alone had come 
in contact with the band beyond. Specific differentiation, that is, the production 
of dark margins, etc., has also halted soon, as we observe that no dark scales 
are present on the last three bands. If development along the same line proceeds 
farther, and by the farther outward growth of the middles of Bands II and III 
and the extension inwardly of the extremities of III and IV, the fascia between 
them become distinctly bent, the pattern of the ground color resembles that of 
oregonensis. There has also been an accompanying gradual deepening of the 
ground color. Specific differentiation at this level over a long period, as evi- 
denced by the black apical spot, has given rise to oregonensis (Fig. 2). If, 
on the other hand, evolution of the first three bands stops at the level of tiliacella 
but continues in the apical four bands until IV, V, VI and VII are continuous 
along the middle of the wing, species of the type of the European L. nicellii will 
be produced. 
