7688 Entomological Society, 



many different plants, the specimens bred differing only slightly in size and depth of 

 colour. And, again, as far as my small experience goes, the species of other genera 

 have each their own food-plant, or perhaps frequent one or two closely allied species. 

 That differences so great as even to be called varieties can be produced by change of 

 food I must believe to be impossible. All who have paid any attention to breeding 

 Lepidoptera will readily say how impossible it is to produce varieties at will, and how 

 an occasional specimen will make its appearance with such peculiarities of form and 

 markings that, had it been taken at large, with no knowledge of its previous history, it 

 would have stood a fair chance of remaining undetermined or described as new, but 

 which has been bred from the same brood of eggs kept under precisely the same cir- 

 cumstances. And certain species of Peronea are familiar instances of the imago varying 

 to such an extent that scarcely two can be found precisely alike, while the larva; feed 

 on the same plant and present no differences. On the other hand, in certain genera, 

 for instance Eupilhecia, in many species the larvae, though reared from the same brood 

 of eggs and fed together on the same plant, will vary as much as the imago of Peronea, 

 yet the perfect insects produced from these are identical in appearance. From these 

 and a thousand other instances that might be cited, it docs appear to me that variation 

 caused by the food of the larva does not exist, except as to size and tone of coloration, 

 and that any differences in the the number, position and direction of fasciae or spots, 

 iu which consist the distinctive characters of most of the Micro-Lepidoplera in question, 

 can be caused by this means is, as said before, open to the gravest doubts. That such 

 variation can be caused in one or two generations seems to be quite impossible ; and, 

 supposing that any influence can be exercised in this way, it could only be in the 

 course of ages, which theory, however ingenious, and perhaps truthful, it may be, is 

 unfortunately from its very nature incapable of proof,'' 



Professor Westwood observed, with reference to the views advanced by Mr. 

 McLachlan, in the paper just read, that he had endeavoured to guard himself from 

 misapprehension in speaking of the modification of species produced by change of food. 

 He had indeed given it as his opinion that such a change was capable of occurrence 

 in certain species, although he was in no position to attest it as a fact. In stating that 

 it was difficult to meet this argument, owing to the minuteness of the Micro-Lepidop- 

 tera, Mr. McLachlan had overlooked the fact of the great variation occurring in the 

 largest species of Papilio, as well as Mr. Bates' statement of the variation of the Ama- 

 zonian butterflies, produced, as had been supposed, by a comparatively small geogra- 

 phical range, but which Mr. Westwood%as inclined to attribute to other causes, seeing 

 that in Africa the same species ranges unchanged over a great part of the continent. He 

 considered that careful experiments as to the powers of modification of species resulting 

 from variations of food would produce important results. He had looked in vain 

 for any structural variation in many of the larvae of the same genera published by 

 Mr. Stainlon, a difference in colour and a variation in the form of the miue or case 

 (all of which might be induced by the variation of the leaves on which the insects 

 fed) being in many cases the only appreciable differences. 



Mr. Desvignes communicated a paper intituled " Descriptions of New Species of 

 Bassus." 



Part IX. of the current volume of the Society's ' Transactions ' was announced as 

 published. — E. S. 



