CAUSES OF MELANISM IN LEPIDOPTERA. 131 



upon the food-plant has more to do with variation — heredity 

 or otherwise — and melanism, than either chemical fumes or 

 coal smoke. If the two latter, how is it that there are not 

 in Lancashire cases of melanism in such insects as Liparis 

 salicis, L. auriflua, Cabera pusaria, &c. ? 



I should like to hear the opinion of such gentlemen as 

 Messrs. Hellins, Buckler, Bond, Gregson, Harwood, Barrett, 

 Green, Crewe, and others of equal observation and practical 

 knowledge. They must have met with many very interesting 

 cases of melanism and variation in their entomological 

 experience, the publishing of which might open our eyes to 

 new iacts, and probably give a clue to some other theory 

 than any yet propounded. 



13, Holgate Road, York, April 14, 1877. 



CAUSES OF MELANISM IN LEPIDOPTERA. 



By E. K. Robinson. 



The most important of these seems to be the con- 

 dition and nature of the food-plant ; for I have noticed 

 that when the larva has been reared upon succulent and 

 overgrown herbage, the imago generally assumes a larger 

 size and paler shade of colour. This appears distinctly 

 in specimens of the common silkworm-moth {Bomhyx 

 mori), whose larvae have for two generations fed upon the 

 juicy lettuce, when placed side by side with others from the 

 mulberry. The silk also produced by the former is inferior 

 and of a pale green tint. Again, most of the marsh moths, 

 and those whose larvae feed on reeds and other plants growing 

 in water, show a large preponderance of white in their 

 colouring. Take for instance the whole genera Nonagria 

 and Leucania. Again, gloomy woods where the air is damp, 

 and the plants bleached and straggling, are the haunts of 

 pale dull moths, such as the genera Acidalia, Cabera, and 

 others. The different varieties of Lomaspilis marginata 

 seem a good instance of the effect of locality ; I have three 

 dark distinctly-marked specimens, ail caught upon a some- 

 what bare hill-side ; and several others with scarcely any 



