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 popuUella (Fig. 27), diaphanella (Fig. 28), 

 salicivorella (Fig. 29), deceptusella (Fig. 30), alnicolella (Fig. 32), alni, incanella 

 (Fig. 34), scudderella (Fig. 35), ledella (Fig. 33), malimalifoUeUa (Fig. 37), cratce- 

 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 carycealhella (Fig. 21), rileyella 

 (Fig. 22), ostrycefoliella (Fig. 23), olivceformis (Fig. 24), ohscuricostella (Fig. 25), 

 kearfottella (Fig. 26), obsoleta (Fig. 41), sexnotella (Fig. 39) and ceriferella (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), sexnotella (Fig. 39) and ceriferella (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), lucidico Stella (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 fasciae. 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 fasciae, the first crossing the wing at the basal fourth, the second at 

 the middle. In obstrictella (Fig. 64), these fascise are almost perpendicular 

 and straight; the pair of white streaks beyond often form a third fascia. In 



