ADAPTATION IN COLORATION. 2I9 



as I have been able to discover, the genus as a whole is almost entirely free 

 from the attacks of insectivorous animals upon the adults. I can, therefore, 

 come to no other conclusion than that the conspicuousness of the coloration 

 of the adult beetles serves to advertise for the mutual benefit of themselves 

 and their enemies their inedible character. 



The larvae of Leptinotarsa also possess striking colors and display them in 

 a most conspicuous fashion upon their food plants. In rubiginosa, rubicttnda, 

 and decemlineata the larvae are bright red ; in diver sa and signaticollis, when 

 mature, they are yellow and black; in lineolata they are banded black and 

 white, and in multitceniata and oblongata, when mature, they are a brilliant 

 yellow. All larvae also possess glands which secrete pungent and ill-tasting 

 fluids, and extrude them on the least provocation. To vertebrate enemies 

 these larvae are quite immune, as I have repeatedly proven with decemlineata 

 by feeding it to fowls, and with multitceniata and oblongata by feeding them 

 to toads and lizards. 



These colors do not, however, afford protection from insect enemies, as I 

 have abundant evidence that the brilliantly colored larvae of multitceniata, sig- 

 naticollis, diversa, undecimlineata, decemlineata, and lacerata are attacked by 

 predacious Hemiptera for the purpose of sucking out the body fluids. How- 

 ever, the attacks of these enemies are of little moment, and do not seem to 

 appreciably reduce the numbers of any species of Leptinotarsa. The Hemip- 

 teron attacks the beetle by making a small puncture and sucking out the 

 haemolymph, and as it does not come in contact with the glandular secretion 

 it is not repelled thereby. Although a considerable number of larvae may be 

 destroyed by these insects, it is the vertebrate enemies that are most effective, 

 and against which protection is really needed. 



In almost all Leptinotarsas it is the mature larvae only that are brilliantly 

 colored. The earlier stages, which are often devoid of bright colors, are pro- 

 tected by their resemblance to their food plant or to other objects in their 

 environment. Thus, in signaticollis and nndecimlineata, the larvae of the first 

 two instars, covered with trichomes gathered from their food plant, crowd 

 closely together so that they resemble withered leaves or dust; while in the 

 last stage they live freely exposed, but are protected by their brilliant col- 

 oration. These conditions will be considered later on under the head of 

 "Protective resemblances in coloration." 



Although I find in Leptinotarsa, in both adults and larvae, the phenomenon 

 of warning coloration present and producing the immunity from vertebrate 

 enemies which the originator of the theory attributed to it, I must acknowl- 

 edge that to find and recognize the phenomenon and its utility in the economy 

 of the species is one thing, but to discover how the various combinations of 

 strongly contrasted colors came about, or how the final adaptation of warning 

 colors to environment was accomplished, is another and entirely different 

 question. Likewise, to explain the observed phenomena and their undoubted 



