26 PROCEEDINGS OP THE ACADEMY OP 



Abboltii, la}' upon the surface of the soil, and after a period of five 

 da3 r s entered the chrysalis form. By comparison with chrysalides 

 which had been divested of their silken coverings, I could not dis- 

 cern more than ordinary variation. These chrysalides developed 

 into male moths. 



That differences occur in the size, shape, and color of cocoons, 

 1 am convinced beyond a doubt. The surroundings of a larva and 

 the quantity of its food, have much to do with the size and con- 

 figuration of its cocoon; while the character and quality of the 

 food affect the color of the same. 



Where the molecules of matter that enter into the physical com- 

 position of a leaf maintain a nearly perfect stability, by under- 

 going few or no re-arrangements, the characteristic color will be 

 reflected. Various circumstances, such as the existence of an acid, 

 tend to bring about these molecular re-arrangements. The punc- 

 ture of a leaf by a Cynip, and the want of healthy action therein 

 by inability to decompose the carbonic acid of the atmosphere, are 

 producing causes. 



We are all familiar with the changes which leaves undergo in 

 the autumn consequent upon the diminished flow of sap into their 

 petioles, and the somewhat lessened vigor of the sun, that source 

 of life and light, passing from green to black through the transi- 

 tional tints of yellow, orange, red, and brown. 



If the colors of leaves are determined in a measure b} r molecular 

 arrangements, why may not the introduction of certain kinds of 

 food into an insect's economy, materially different from what it 

 has been accustomed to, so impress with change the organs whose 

 functional business it is to elaborate the fluid which it utilizes 

 in the manufacture of its cocoon as to reflect different colors or 

 shades of colors ? I can see no difficulty in the matter. Indeed, 

 it has been shown that if the mulberiy silkworm, Bombyx mori, 

 be fed upon its natural food for a limited period, and then upon 

 the leaves of different plant-species, it will elaborate a thread dis- 

 similar in color to what is ordinarily produced. To the success 

 of this experiment it is not absolutely essential that the larva 

 should be fed upon its natural food primarily as asserted, as some 

 late experiments of mine testify. 



Where the essential conditions are present, such as abundance 

 of leaves of natural food-plant, and a freedom upon the part of 



