226 COI.ORATION IN I.EPTINOTARSA. 



say it is due to the morphological and physiological constitution of the species, 

 to ids and determinants, or to internal perfecting forces, all of which explana- 

 tions are attempts to appear wise when we are ignorant. 



When the facts as to the source of the color-producing cells of the wings 

 and their general behavior in ontogeny are joined to those of the variation 

 and ontogeny of coloration — the production of stripes, bands, or spots, or uni- 

 colorous conditions — they enable us to gain a clearer comprehension of color- 

 ation than is otherwise possible and to understand how orthogenesis is pro- 

 duced in variation and evolution, yet we are still ignorant as to the causes. 



Let us examine our material in the light of the above conclusions, and we 

 shall be better able to explain the conditions found in elytral coloration. In 

 calceata, dilecta, lineolata, and typographica (plate 23, figs. 13 to 16) we 

 see species formation along a definite line and a distribution from southern 

 Mexico to Texas. In this series the evolution, variation, and distribution all 

 show indisputably the existence of orthogenesis; for it is highly improbable 

 that the conditions could be due to chance. Finally, when we take into 

 consideration the fact that the entire genus shows these conditions of dis- 

 tribution, variation, and coloration there exists not the slightest doubt of 

 orthogenesis in the genus Leptinotarsa. 



The existence of a fundamental color pattern which each species or genus 

 variously modifies in its own fashion has been proven, but why each species 

 should do thus or so with this general plan of coloration is exactly the same 

 problem as why species do thus and so with the fundamental plan found in 

 other organs. This is the problem of the origin of species, and the explana- 

 tion of the existence of the general plan of each system of organs belongs to 

 the still more remote problem of the origin of phyla. 



Although we can not at present explain the observed conditions otherwise 

 than through speculation, we have gained evidence which is of value in the 

 interpretation of the phenomena of distribution, variation, and coloration. 

 We might examine other characters in the genus, such as the epicranium, 

 pronotum, legs, etc., but we should consume space and time unnecessarily and 

 arrive at the same conclusion. 



It must be admitted that there exists in Leptinotarsa a race tendency, no 

 matter how it may be accounted for, which from the general system of color 

 centers existing in the genus as a phyletic character produces coloration of a 

 certain type, spots, bands, stripes, or combinations thereof, which type is 

 variously modified by each species. The study of coloration deals largely 

 with these racial tendencies, and leads to the following general conclusions : 



(i) Centers of color origin. — In ontogeny and in evolution (species forma- 

 tion) color appears first in centers which upon the body are metamerically 

 repeated spots and upon the wings are either spots, stripes, or bands. In devel- 

 opment the anterior or proximal centers develop first because they are first 



