124 COLORATION IN LEPTINOTARSA. 



most widely distributed of all insect colors. The results of their examination 

 have been summarized in the form of a table, which is here reproduced : 



f 



Chemico- 

 physical 



(Reflection, ) Colored surface h r n 3 n V 1 Caused by thin, polished lamella:, 



. < pigmental < with polished \ vellnws f or b ^ a poshed surface over a 

 ' (. colors. I appearance. reds layer of pigment. 



(41 /Retraction, pig- > M , t _ 111 . --inrs 1 Caused by refractive lamellee over a 



(0 M mental colors. ] Metallic colors. | layer of absorptive pigment. 



(nffrartinn nio- l (Caused by surface structures, pits, 



colors. I W mertilcolore Iridescent colors. 1 ridges, stria:, or refractive lamella; 



(_ over an absorptive pigment layer. 



J Various iridescent, metallic, opales- "1 ~ cj i , , * 

 cent colors in which colors of classes [ Co T " ^rt 't r ! y r If r 

 (a), (*), and (c) arc combined in one J 'Xrr?X .'? w f 

 L I color effect. J other orders of insects - 



DEVELOPMENT OF COLORATION. 



The ontogenetic development of color and color patterns in insects has been 

 studied most in Lepidoptera and especially in the wings. The earliest studies 

 of note were those of Schaffer, von Bemmelen, and Urech. These were fol- 

 lowed by the more elaborate researches of Hasse, Mayer, and von Linden. In 

 the other orders of insects studies have been made by Kunckel de Herculais 

 in Orthoptera, Tower in various orders, but especially in Coleoptera, and 

 Enteman in the hymenopterous genus Polistes. 



The studies upon the origin of color in the wings of Lepidoptera have 

 shown that there is a regular order of development, not only of colors, but 

 also of the areas in which spots and stripes appear. The wings, which are 

 colorless at first, become opaque, yellowish, or light drab, beginning first near 

 the base of the wing and spreading distalward. Soon spots, stripes, and adult 

 markings appear, at first proximad, then more and more distad, then between 

 the nervules, and, last of all, upon the nervules. First the purely pigmental 

 or chemical colors develop, and these are followed by the chemico-physical. 

 Upon the body in various orders of insects I have found, as has also Ente- 

 man, that the color develops in segmentally arranged spots located upon im- 

 portant sclerites, usually over muscle insertions, and that from these centers 

 it spreads out, giving a surface either uniformly colored or spotted, if the 

 primary centers remain unfused. Development proceeds in general from 

 before backward, and from proximal to distal. The order of succession in the 

 colors has been found by these authors to be much the same as that in the 

 wings of Lepidoptera ; the lighter and simpler colors appear first, followed by 

 those which are darker and more complex, and these by the appearance and 

 development of the chemico-physical colors. The ontogeny of larval and 

 pupal coloration has not been studied. 



PURITY OF INSECT COLORS. 



The purity of insect colors has been investigated by Mayer (1897), who 

 has found that there are few or perhaps no pure colors in butterflies. All the 

 examinations made by this author have shown that a given color is in reality 



