EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 107 
In all, the larva is of the so-called cylindrical type, which agrees well with the 
usual type of lepidopterous larva. During the first three instars, in which the 
extent of the mine is gradually inereased by a loosening of one epidermis, the 
larva has a characteristieally flattened shape, with flat 
head and projecting mouth-parts. After the third moult, P< 22-2 E 
the larva assumes the normal eylindrical shape and the کچ‎ Y 
= — 
mine becomes tent-like by a fold in the loosened epider- : 
mis. Тһе larva then consumes the greater part of the — —— — MÀ 
. parenchyma within the area occupied by the mine. The 
Fic. 3. Venation of Cre- 
mastobombycia, 
pupa, except that of one species, is always formed within 
the mine and may or may not be enclosed in a cocoon. 
The forewings of the imagoes are marked by various tions of white 
transverse fasciz and streaks on a yellowish ground color. These white marks 
are bordered along their inner edges by dark brown or blackish scales; some- 
times, but to a less extent, dark scales may also appear along their outer edges. 
The hindwings are unicolorous. 
Our American species while conforming in all structural characteristics to 
those of Europe, fall naturally into two groups; one of these agrees closely in 
structure of larva and imaginal markings with the European type just described; 
the other has what has been termed the “flat larva,” and the imagoes produced 
from such larvæ can always be sharply distinguished by their markings from the 
species of the “cylindrical-larval group." The “flat larva" retains the flat 
shape, which is characteristic of the first three instars of the ‘“eylindrical-larval 
group," through the fourth, fifth and sixth instars, only assuming the cylindrical 
shape and an approach to normal mouth-parts with the last moult. By some 
systematists, the persistence through three additional larval instars of the curious 
modification of the mouth-parts, which is in fact an adaptation for loosening 
the epidermis, has been regarded as a suff cient ground for the generic separation 
of this group, and the name Cameraria Chapman has been applied to it (Chap- 
man, 02). The other view, which regards the modification of the mouth-parts 
merely as an adaptation for a partieular mode of life, and not a character indi- 
cating the natural separation of that group from one with which the imagoes 
agree in all structural details, has been presented in the Canadian Entomologist 
for December, 1909 (Braun, ’09). 
The mines of the “flat-larval group” are always found upon the upper side 
of the leaf. The increase in the extent of the mine continues through six instars, 
the larva consuming only a few layers of cells in front of it. For this reason, 
the parenchyma within the mine is never entirely consumed and the mine 
rendered semitransparent, as is the case in mines of the " eylindrieal-larval 
group." During the seventh instar, the larva does not feed; the time is occupied 
in preparation for the pupal state. Where the imago is to emerge the same 
summer, most of the species spin cocoons. The cocoon is a flat, oval sheet of silk 
attached around its edge to the floor of the mine, the epidermis above being 
Lc 
