112 EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 
minor ones, since the general plan of coloration has been already determined. 
Where a group of species has branched early from the main stem, the individual 
species within it will be found to be less closely related; the longer period of 
time allowed for differentiation within the group has given opportunity for 
greater divergence of the individuals composing it. 
In general, no effort has been made to discuss the minute characters separ- 
ating the species. Such characters and their processes of differentiation are 
more properly discussed later. 
Leaving out of consideration for the present the species of the subgenera 
Porphyrosela and Cremastobombycia, the main branch of the genus may be 
divided, as has been mentioned earlier in this paper, into two natural divisions, 
sufficiently distinguished from one another by the type of larva and by the 
position with respect to the white fascize and streaks of the dark scales bordering 
them. 
In the division whose larva in the later stages is of the normal cylindrical 
type, when a dark margin occurs on but one side of a white mark, it is present on 
the internal edge. In the majority of the species, this margin is the only one 
present; in some species, however, external margins have developed adjacent to 
some or all of the streaks. "The external margin is, as a rule, considerably paler 
and less complete than the internal one; in a few cases, where both are equally 
well developed, other characteristies will leave no doubt of the division to which 
any species belongs. For convenience of reference, this division has been 
designated Division I. "The species are illustrated on Plate III. 
Several well-defined groups are recognizable. Some of these include a 
considerable number of species, showing close intergradations and indicating 
their origin from a common ancestor at a no very remote period. Other species 
seem to stand apart, showing no very clear affinities with any of the existing 
species. : 
One group, comprising L. tiliacella (Fig. 1, Pl. III; Text Fig. 7), oregonensis,! - 
affinis, tritenianella (Fig. 5), ostensackenella (Fig. 7) and maricella (Fig. 8) as 
typical forms, and fragilella (Fig. 3) and celtifoliella 
ı.9, ¥! A (Fig. 4) as extreme deviations from the typical, is char- 
p acterized by the presence of at least two complete white 
transverse fasciz, the first crossing the wing at about 
the basal fourth, the second near the middle. 
In tiliacella (Fig. 7), the ground color is a very pale 
golden; a spot at the base of the dorsal margin is white; the two fasciz are almost 
straight, the first but faintly dark margined. At three-fourths of the wing length, 
there are two white dark-margined spots, corresponding in position to a third fas- 
cia, very narrowly separated by pale golden scales which unite with a pale band 
of the ground color beyond. Then follows a fourth white fascia, separated from 
the apex of the wing by a few pale golden scales which mark the position of a band 
‘1 [t was impossible to obtain figures of L. oregonensis, affinis, occitanica and alni. 
ДІ IV 
12 - : 
ЭА Куи ае ү UL Tee T TIME TENE NETTE a ИРИРЕК РИИ TD 
OTT à T wen T جن ف‎ Ал 
E ESE dct O CO E SL N DT E 
