78 THE ENTOMOLOGIST S RECORD. 



large quantity of smoke, fumes, etc. which of late years have 

 been developed in Southern Lancashire: — "This may have 

 effected a change in the climate, as well as deposited on the 

 leaves of trees and foodplants of Lepidoptera, matter which 

 may possibly cause some white insects to become gradually 

 black, through being swallowed by the larvae with their food." 

 This, I believe, would have no effect on the larvas themselves, 

 as far as colour is concerned. Phytophagic varieties are, as I 

 have before repeated, mainly ^ those of size, and I fail to see, 

 on ordinary physiological grounds, how the colour could be 

 affected in this way. Dr. White also writes in a very 

 interesting paragraph on this subject {Entomologist, x., p. 

 128): — "In the same way, the foodplants may, on certain 

 soils, affect the colours of the insects ; but if it is so at all, 

 it is probable only in a few cases ; the influence of the food- 

 plant upon the colours of insects seems not to be very great." 

 Mr. Prest, dealing with the same subject {Etitomologist, x., p. 

 130) writes : — " I do not think that either chemical fumes, or 

 coal-smoke can have any influence in our district of York- 

 shire." He then runs through a list of species which are 

 melanic in Yorkshire, and writes : — " From these facts I form 

 my opinion that soil in its action upon the foodplant has 

 more to do with variation — heredity or otherwise — and 

 melanism, than either chemical fumes or coal-smoke." At 

 p. 131, Mr. E. K. Robinson looks upon the foodplant as 

 being the main agent, and instances the Leucaniidce in 

 marshes, entirely overlooking the protective resemblance these 

 species bear to the nodes on the reeds, etc., on which they 

 rest head downwards. He also states as a fact that " food 

 in a semi-withered or dry condition produces moths of small 

 size ; for Aviphidasys betularia thus fed becomes in a few 

 generations completely black ; and by the same means the 

 proportion of black to white in Abraxas grossidariata and of 

 brown and black to white and red in Chelotiia caia, is largely 

 increased." I do not know that there is the slightest founda- 

 tion in fact for supposing that any of the three species 

 mentioned are influenced directly in the way suggested by 

 Mr. Robinson, nor does he offer any further proof of his state- 

 ments, other than thus giving most positively his own opinion 

 on the point. He sums up his arguments as follows: — " (i). 

 A large percentage of water in the tissues of the foodplant 



1 Unless the species feeds on different foodplants which have a very different 

 chemical composition. — J.W.T. 



