Insecta. 277 



piain the origin of the different color patterns. These processes are stated thus: 

 (a) The middle portion of a band may be produced distally until it comes in con- 

 tact with the band beyond it. (b) The extremities of a band may be broadened 

 by being produced proximally. (c) The extremities of a band may be narrowed 

 by the retraction of pigment from their outer edges. The particular result in any 

 case, that is, the configuration of the color areas, is due to the manner and extent 

 of the action of these processes. These bands either in their primitive or modi- 

 fied shape, constitute the ground color. Upon this ground color, a second darker 

 series of elements, the markings proper, also usually transverse, are superimposed. 

 The different levels at which evolution in the pattern of the ground color has 

 halted are the important factors in determining the phylogenetic sequence of large 

 groups; the particular colors and the markings determine the positions of the 

 species within those groups. Their appearance of this marking is probably due 

 to physiological factors within the organism itself, and is independent of external 

 conditions. In the ontogeny, the relative time of appearance of the dark margin 

 of any band is dependent upon the thime when the edge of that band became 

 fixed in the phylogeny. Before dark margins can develop, the edge of a band 

 must have remained fixed for an appreciable time. Hence, where bands have been 

 laid down late or have reached their present configuration late in racial develop- 

 ment, the dark margin will develop at a correspondingly late period in onto- 

 genetic development. A dark marking once permanently established in the race 

 tends to reappear independently of the ground color, so that later suffusion of 

 the unpigmented area contiguous to it with ground color, or the shrinking away 

 of the ground color, does not affect its permanency. Later in phylogenetic history, 

 additional dark markings, other than those contiguous to unpigmented areas, may 

 appear. The most far-reaching and widespread changes have taken place toward 

 the base of the wing proximal to the transverse vein. The final result is the 

 production of a uniform ground color which will be attained earliest near the 

 base of the wing where evolution has proceeded most rapidly. This observed 

 evolution in the pattern of the ground color suggests that the uniform yellowish 

 ground color which suffuses the wing in the higher Lepidoptera, beginning at the 

 base and spreading distalward, is the outcome of a phylogenetically older type 

 of markings, originally banded, and later fused to a uniform color, and that the 

 markings are a second series superimposed upon the first. The observations made 

 are held to point clearly to the conclusion that the evolution of the color pattern 

 in Lithocolletis has been orthogenetic. ' Pearl. 



836) Carpenter, (j. D. H., Pseudacraea eurytus hobleyi, Neave; its forms 

 and its modeis on Bugalla Island, Lake Victoria, with other mem- 

 bers of the same combination. In: Trans. Entom. Soc. London, Bd. 1913, 

 Heft IV, S. 606—645, 3 pl., 1914. 



It has already been shown that the several forms of Pseudacraea, described 

 as eurytus, hobleyi, terra, öbscura etc., each of which mimics a different species 

 of Plancma, are Polymorphie forms of one species, since the various forms oeeur 

 together among the offspring of the same parents. On the mainland of Uganda 

 these forms are very distinet, intermediates, though not unknown, are very rare, 

 and in numbers of individuals the Plancma modeis are far more numerous than 

 the Pseudacraea mimics. The present paper shows that on Bugalla Island, in 

 Lake Victoria, the Plancmas are relatively scarce, much less common than the 

 Pseudacraeas, and in connexion with this, intermediates between the different 

 forms of Pseudacraea are frequent. It is suggested that on the mainland the in- 



