116 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 
streaks on the dorsum, the first usually very oblique, the second, which is placed 
at the tornus, often nearly perpendicular, and four costal streaks (rarely five as 
in populiella and rileyella). These are populiella (Fig. 27), diaphanella (Vig. 28), 
salicivorella (Fig. 29), deceptusella (Fig. 30), alnicolella (Fig. 32), alni, incanella 
(Fig. 34), scudderella (Fig. 35), ledella (Fig. 33), malimalifoliella (Fig. 37), crate- 
gella (Fig. 36) and propinquinella (Fig. 38), in which the black scales in the apex 
are not massed to form a circular apical dot; and caryealbella (Fig. 21), rileyella 
(Fig. 22), ostryefoliella (Fig. 23), oliveformis (Fig. 24), obscuricostella (Fig. 25), 
kearfottella (Fig. 26), obsoleta (Fig. 41), sexnotella (Fig. 39) and eriferella (Fig. 
40), in which a number of small black scales in the apex are grouped into an 
almost circular, definitely outlined, apical spot. In obsoleta (Fig. 41), this spot 
is very ill-defined, as are all the other markings. With the exception of the 
three last mentioned species, a white median basal streak extends to about one- 
third of the wing length. This streak may be margined above and sometimes 
around its tip with dark scales. In some of the species, there is, on the dorsal 
margin, a small white spot, often extended almost to the base of the wing and 
with its outer edge about midway between the base of the wing and the first 
dorsal streak. In a few cases (e. g., incanella (Fig. 34)), this spot is indistinctly 
margined on its inner side by a short oblique line of darker scales. In obsoleta 
(Fig. 41), seznotella (Fig. 39) and «riferella (Fig. 40), the entire basal portion 
of the wing is without markings, the ground color extending uniformly over it. 
Lastly, there is that subgroup of species in which there is but one margined 
dorsal streak and that one is situated at the tornus; the basal portion of the 
wing is, to a great extent, shining white, and any colored markings present are 
longitudinal. These are trinotella (Fig. 47), quercialbella (Fig. 46), clemensella 
(Fig. 45), lucidicostella (Fig. 44) and argentifimbriella (Fig. 43). Phylogenetically 
considered, albanotella (Fig. 42) should be included here, as representing an earlier 
stage in the process resulting in the production of these five species. In this 
species, a first dorsal streak is defined by an incomplete margin not reaching the 
dorsum. 
In Division II of the genus, illustrated on Plate IV, where the modified flat type 
of larva persists through six larval instars, the chief aggregation of dark scales is 
on the outer side of the white streaks and fascie. Where an additional margin 
occurs on the inner side of the white markings, the outer one has broadened con- 
siderably and is often prolonged at the angle of a fascia as a dense aggregation of 
dark tipped scales. There seems to be less tendency in this group toward the con- 
centration of dark scales in the apex over a definitely outlined area; the tendency 
is rather for all the scales to become dark tipped, producing an evenly dusted 
effect. As in Division I, several groups of species are recognizable. 
In one group, there is a tendency to preserve, either straight or angulated, 
two white fasciz, the first crossing the wing at the basal fourth, the second at 
the middle. In obstrictella (Fig. 64), these fascie are almost perpendicular 
and straight; the pair of white streaks beyond often form a third fascia. In 
TOES 
Ec eee 
