IDD COLORATION IN LEPTINOTARSA. 



It has been shown that color in these beetles is limited in its appearance to 

 definite centers, and that all patterns must, as far as is known, originate from 

 continuations of these centers, so that color patterns are in a degree limited. 

 This character is one of such wide distribution in insects that I consider it to 

 be a character of the phyletic race one that is so firmly fixed in the constitu- 

 tion of the tracheate protoplasm that it can not be eradicated. It is one of 

 those phyletic characters whose origins are unexplained excepting by theory. 

 In the Coleoptera, and especially in the Chrysomelidas, the existence of these 

 centers in development is beyond doubt. Their presence gives to each species 

 a like background out of which each species creates its own distinctive color 

 pattern. That is, all start in ontogeny endowed with an identical arrange- 

 ment of color-producing centers, which become variously modified, sup- 

 pressed, or accentuated in different stages and in different species. 



Strong evidence against the idea of specific ancestral influence is found in 

 the three species iindecinilincata, multitccniata, and oblongata, L. undecim- 

 lineata is undoubtedly the ancestor of multitccniata, and oblongata arose 

 from the latter. On plate 17, figs. 1 to 3, are given the three stages of 

 uudeciniliueata, beginning with a condition which is generalized and ending 

 with that shown in fig. 3. L. multitccniata (figs. 10 to 12) never goes as far 

 in the modification of its color pattern as its ancestor undecimlincata, while 

 oblongata starts in life with a condition far beyond its parent in its specializa- 

 tion. Here is a condition difficult to explain upon the basis of a literal inter- 

 pretation of the biogenetic law, of a species starting its ontogeny far in 

 advance of the adult parental condition. This surely is Hyatt's idea of accel- 

 eration in development carried on with great speed. Now, I find that the 

 cells which form the centers of coloration are developed in the embryo of 

 oblongata, but that they remain quiescent until the pupal period, when they 

 become active and produce color areas in the proper place, as is shown on 

 plate 20. I am not able to understand how this condition found in oblongata 

 can be the result of ancestral influence. Surely there are no indications of the 

 process in the parent, and in the grandparent species the same modifications of 

 color have taken place in the larva in the second instar (fig. 2). The extreme 

 advocate of the law of biogenesis will in this instance claim that through 

 acceleration in development the earlier stages have been dropped off in the 

 embryo, so that the larva of oblongata starts in life with the mature color pat- 

 tern of its grandparent species. This would all be very well were it not for 

 the presence of the color-forming cells in the late embryo, and the fact, above 

 mentioned, that they remain inactive throughout the larval life and become 

 active and produce color areas in the pupa. This can not be successfully 

 explained by the theory of temporary retardation of development, because we 

 have the phenomenon slightly varied in many species. Nor do I see how how 

 the idea of the recapitulation of the immediate ancestral stages in growth can 



