ON SOME CAUSES WHICH SEEM TO OPERATE IN THE 

 PRODUCTION OF VARIETIES IN LEPIDOPTERA. 



By S. L. Mosley. 



(Concluded.) 



One exciting cause in the production of varieties, no doubt, is the 

 food-plant of the larvae, but entomologists make mistakes in supposing 

 that wonderful results can be brought about by this means in a single 

 generation. Bomhyx quercus fed upon ivy, has a tendency to becofue 

 destitute of scales ; bullfinches fed upon hemp seed become black, and 

 primroses planted in cow-dung turn red. Several closely allied species 

 of moths might be referable to a change in the food-plant of the 

 larvae. Not that I wish to question their distinctness as species, but 

 I think that a forced or accidental change in the food carried on from 

 generation to generation might have been a means of bringing about 

 their differences. I may instance E. linariata 2iTi^ jmlcliellaia^ Procris 

 statiees and geryon ; and we seem to have something like proof in the 

 case of E. minutata and knaiitiata, for in the place where knautiata 

 is taken they tell us that ling and minutata used to be found, and 

 that the ling has since disappeared, and it seems probable that the 

 insects were driven from the heather to the flowers of Knautia arvemis^ 

 and that hiautiata is a species as good as some that I might mention, 

 caused or greatly influenced by a change in the food of the larvee. I 

 grant that some experiments seem to show that food has no influence 

 in the production of varieties. For instance, Mr. Sidebotham 

 {Sc. Gos., Dec, 1869) procured 2,500 larvae of C. caja, and fed them 

 in six different lots — one on willow, one on butter-burr, one on haw- 

 thorn, one on plum, one on dock, and another on various kinds of low 

 plants. The result of this was, that " the variations in colour and 

 markings were not to be traced in any case to the food." Another 

 similar attempt is recorded (Ent. ix., 251) from France, in which 

 5,000 larv^ of 0. caja were obtained, and fed in different lots on 

 walnut, horse chestnut, sumach, box, celandine, carrot, and lettuce, 

 and some were reared in complete darkness. But all this proved 

 nothing further than that those fed upon lettuce were dull, discoloured 

 specimens, which might have ended in something if lettuce had been 

 continued for a few generations ; for we generally find that those 

 insects which feed upon succulent plants ha\'ing a great deal of water 

 in their tissues, or which frequent marshy land, are pale discoloured 

 'N. S., YoL. v., Dec, 1879. 



