MOTHS AND BUTTERFLIES. 181 



substance is skimmed off and proves a valuable var- 

 nish. I was told that the Japanese use this to var- 

 nish their finest fancy articles. 



Eaising caterpillars for the purpose of obtaining 

 from them perfect butterflies or moths, is not only an 

 agreeable and instructive operation for young pupils 

 in their leisure hours, but it has often been a very lu- 

 crative business. In Altona, in Denmark, I became 

 acquainted with a gentleman who raised in his conser- 

 vatory several species of the large moths, natives of 

 North America, as the Cecropia, Luna, Polpyhemus 

 and Promethea, which he sold readily at two dollars 

 apiece, and of which he raised on an average a thou- 

 sand specimens a year. 



Caterpillars are of quite an important use to man, 

 as the principal food of birds, and the amount of 

 good they do in yielding up their lives as nourish- 

 ment for others, would astonish one unaccustomed to 

 reflect upon the subject, and really goes far towards 

 compensating the injury they do to vegetation. There 

 are at least 1200 species of Lepidopterous insects in 

 existence, and as each female lays on an average 

 three hundred eggs, half their number, viz. : 6000 

 females will produce 1,800,000 caterpillars, in the 

 seccond generation, 180,000,000, and in the third, 

 27,000,000,000. 



If such an immense multiplication of so voracious 

 an animal were to be continued ^without any check, 



