﻿i£8 THE ENTOMOLOGIST. 



Two other reasons for failure at sugar have also suggested 

 themselves to rue, namely, the increasing mildness of our winters, 

 and the frequent gales and heavy rains in the spring. In the first 

 case it seems to me that numbers of larvae must hatch from the 

 egg long before there is the slightest chance of their obtaining 

 their particular food, and these therefore doubtless perish in large 

 quantities ; and secondly, those laivse which are still small must 

 often be washed off their food-plants and drowned, or are blown 

 from the trees by the strong winds, only to die of starvation. 

 The question is an interesting one, and I therefore hope, with 

 Mr. Anderson, that we may see the opinions of some of our 

 leading entomologists on the subject. 

 Groornbridge, Sussex, Feb. 18, 1890. 



CONTEIBUTIONS to the CHEMISTEY of INSECT COLOUES. 

 By F. H. Perky Coste, F.O.S. 



Preliminary Notices. 



I. 



The experimental investigation of the chemical characters of 

 those colours whose superb brilliancy or delicate tones, as dis- 

 played in tens of thousands of insects, never fail to evoke our 

 enthusiastic admiration and afford us a source of unflagging 

 delight, might, indeed, be thought to offer an enticing field for 

 scientific research. Reasoning deductively, and as merely ento- 

 mologists, from the data afforded us by the colour variations 

 occasional in all insects ; by the different forms that the same 

 species may take in different countries ; by the existence of 

 intermediate* species, forming a connecting link between two 

 quite differently coloured species ; by the comparison of allied 

 species in which similar markings are dissimilarly coloured ; and 

 lastly, by the actual evolution of colour in the same individual 

 insect that we can occasionally observe ; f reasoning, I say, from 

 all these data alone, we may draw certain conclusions as to the 

 evolutionary rank of some insect colours. Notably is this 

 possible with regard to reds and yellows ; and the views already 

 advanced, for instance, by Mr. T. D. A. Cockerell, in the pages of 

 the ' Entomologist ' and elsewhere, will be found anon to be con- 

 firmed by the results of direct experiment. But this question of 

 the evolution of red colour in insects was, perhaps, the plainest 

 sailing of all ; true we may farther proceed to theorise on the 

 relations of yellow and white, but here the way is apparently not 

 so clear ; and the danger of resting satisfied with theoretical 

 results, unverified, however satisfactory they seem, becomes soon 



* I speak here of colour only. 



t E.g., in the newly emerged imagines of atalanta and caia> 



