EVOLUTION OF COLOR PATTERN IN LITHOCOLLETIS. 123 



3. Observations. 



Two factors were taken into consideration in determining the choice of species 

 to be studied, namely, the general type of adult marking and the presence or 

 absence of certain characters such as an apical spot or dark marginings adjacent 

 to white streaks or fascise. The object of the research is twofold: (1) to deter- 

 mine, if possible, the primitive or fundamental color pattern and its mode of 

 transformation into the adult pattern and (2) to determine the relative time of 

 appearance and manner of development of the various dark markings, the 

 characters referred to above. 



The evidence furnished by the development of color in the pupal wings 

 taken in conjunction with a comparative study of the adult markings has con- 

 vinced me that the primitive color pattern is composed of a series of uniformly 

 colored pale yellow ban ds, seven in number, placed transversely on the wing and 

 separated from one another by white fasciae (unpigmented areas) (Fig. 8) . These 

 bands are typically straight and, with the exception of 



the first, cross the wing almost perpendicular to the mar- j, ^^ ^ v vi 



gms. The bands, when present m their primitive con- ■ ' ' 



dition, have certain defined positions. Their hypothetical 

 typical positions are illustrated by Fig. 8. In what fol- '" ^ 



lows, it will be noticed that there is a definite relation _ ^^ ,.,... 



. . Fig. 8. Hypothetical primitive 



01 bands to veins. Band I occupies the extreme base color pattern of the forewing of 

 of the wing, beginning at the base of the dorsum and Lithocoiietis. 

 broadening on the costa; the white streak which sepa- 

 rates it from Band II passes obliquely from the base of the dorsum toward 

 the costa, lying over the point of origin of the tubular portion of the lower 

 median vein. Band II crosses the wing on the basal side of the tip of vein 

 12; the position of the white fascia which separates it from Band III seems 

 to be determined rather by the point of origin of the tubular portion of the 

 upper median vein than by the tip of vein 12, as this vein often extends con- 

 siderably beyond the origin of the upper median vein without causing a cor- 

 responding broadening distally of the second band. It sometimes happens 

 that vein 12 is unusually short, and then the white fascia lies over its tip and 

 over the origin of the upper median vein. On the costa, the inner border of 

 Band III hes just beyond the origin of the upper median vein, and on the dorsum, 

 the outer border extends almost to the tip of vein 16. Band IV crosses beyond 

 the tip of vein 16 and hes over the bases of veins 10 and 2, its outer border being 

 just within the tips of veins 10 and 2. Band V on the costa is placed between 

 veins 10 and 9, on the termen between veins 2 and 5 and lies over the transverse 

 vein. Band VI is placed between veins 9 and 7 on the costa and beyond vein 5 

 on the termen. Band VII crosses the apex of the wing. Thus it will be seen 

 that the position of the bands is largely determined by the position of the longi- 

 tudinal nervures, the tips of the veins marking the extremities of the unpig- 

 mented fasciae separating the bands. In no case in the adult has this pattern 



