114 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 
type of marking. There are two lustrous white fasciæ, dark margined on both 
sides, on a dark reddish brown ground color, showing a deep purple metallic 
luster at the base of the wing. 
In another group of species, the median fascia only has been preserved, 
either in its primitive almost straight condition or has become angulated. Most 
of the species bear no close relationship to one another, and it would seem, there- 
fore, that the group is merely an artificial one and that the characteristic of a 
median fascia is one which appears in several divergent lines of development. 
The species which may be included in this group for purposes of discussion are 
the following: L. morrisella (Fig. 48), uhlerella (Fig. 49), lucetiella (Fig. 51), 
symphoricarpella (Fig. 54), gemmea (Fig. 53), martiella (Fig. 52), celtisella (Fig. 
56) and apicinigrella (Figs. 55a, 550).  Robiniella (Fig. 50) shows a very clear 
natural relationship with the first two mentioned species, and differs from them 
only by the separation of the median fascia into a pair of opposite costal and 
dorsal streaks,' and the obliteration of the first dorsal streak by dark scales. 
Morrisella (Fig. 48,), uhlerella (Fig. 49) and robiniella (Fig. 50) are a 
remarkably homogeneous triad of species; the figures will suffice to give a clear 
idea of their characteristics. In lucetiella (Fig. 51), the entire basal half of the 
wing is white, with the exception of a longitudinal streak from the base follow- 
ing the course of the upper median vein; the apical half of the wing closely 
resembles that of tiliacella (Fig. 7). In symphoricarpella (Fig. 54), the basal 
half of the wing is of the golden brown ground color; the white streaks over 
veins 9 and 5 are lacking. In martiella (Fig. 52) and gemmea (Fig. 53), there 
is a white basal streak; in gemmea a white spot on the dorsal margin occupies 
a position nearly corresponding to the extremity of the first fascia. In these 
two species, as in morrisella, uhlerella and robiniella, a group of small scales in 
the apex forms the black apical dot.  Celtisella (Fig. 56) and apicinigrella (Figs. 
55a, 55b) are characterized by the presence of an acutely angled fascia and a 
median white basal streak. In celtisella, the dorsal margin is also white from 
the base to the fascia. Apicinigrella is an extremely variable species; sometimes 
the fascia is broken in the middle; an extreme aberrational form is represented 
by Fig. 55b. 
Basistrigella (Fig. 57), although a somewhat isolated species, is perhaps 
most closely related to celtisella (Fig. 56) and apicinigrella (Figs. 55a, 55b) of 
the above group. The median pair of streaks are of equal width throughout 
and each is extended at its extremity along the margin to the base. 
Bataviella (Fig. 58) stands entirely apart from any of the species of 
the American fauna; there are, however, several closely related species in the 
European fauna. The white spot which was present at the base of the dorsal 
margin in tiliacella and did not reach the costa, is here often extended entirely 
! The terms “costal streak” and “dorsal streak" are used to designate the white and usually 
triangular spots situated on the costa and dorsum respectively. 
? The “basal streak” is the white longitudinal line beginning at the base of the dorsum and 
extending along the middle of the wing for about one-third its length. 
