114 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 



type of marking. There are two lustrous white fasciae, dark margined on both 

 sides, on a dark reddish brown ground color, showing a deep purple metaUic 

 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 apicinigreUa (Figs. 55a, 556). Rohiniella (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 rohiniella (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 rohiniella, a group of small scales in 

 the apex forms the black apical dot. Celtisella (Fig. 56) and apicinigreUa (Figs. 

 55a, 556) 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. ApicinigreUa is an extremely variable species; sometimes 

 the fascia is broken in the middle; an extreme aberrational form is represented 

 by Fig. 556. 



Basistrigella (Fig. 57), although a somewhat isolated species, is perhaps 

 most closely related to celtisella (Fig. 56) and apicinigreUa (Figs, b^a, 556) 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 



1 The terms '^ costal streak" and '^ dorsal streak" are used to designate the white and usually 

 triangular spots situated on the costa and dorsum respectively. 



2 The ''basal streak" is the white longitudinal hne beginning at the base of the dorsum and 

 extending along the middle of the wing for about one-third its length. 



