THE COTTON-WORM. 147 



tribe, that the egg must be deposited on the leaf on which the 

 larvae are to feed ; and the reason is very plain, for these larvae, 

 when first hatched, are minute living points, of an exceedingly 

 helpless nature, almost devoid of locomotion, or possessing it 

 in too small a degree to enable it to go in search of its food. 

 But let us suppose that the egg does survive the winter; how 

 does it happen that when the worm first makes it appearance, 

 it is found on the very summits of the cotton, instead of the 

 lower branches ? parts that it would reach the soonest, if it 

 proceeded from the ground upwards. 



The plialena mosi, or silk-worm, is an insect of the same 

 genus as the cotton-fly, and whose habitudes are very much 

 the same as the latter, tropical in its nature, confining itself to 

 a particular vegetable, the different species of mulberry, and 

 being short-lived in the chrysalis, remaining in this state but 

 fifteen days. At the approach of winter, when the mulberry 

 trees cast their leaves, and remain leafless for many months, 

 these insect, in our climate, would all perish, were they left 

 to themselves. But art, in this respect, has triumphed over 

 nature ; for the silk grower at a certain season gathers a parcel 

 of eggs, and places them in a cold dark place until the mul- 

 berry tree shall again afford them food in the spring, and in 

 this manner they are perpetuate^, and this is the only possible 

 way that they could be preserved here. They are like some 

 tender exotic, which flourishes as long' as the warmth of the 

 hot-house affords them a congenial atmosphere, but perishes 

 if left to buffet the rigors of winter. 



Proposition second. Here I contend that when an insect 

 is a native of, or naturalized, in any country, they are always 

 governed by some invariable laws which determine their ap- 

 pearance. The grasshopper is annual, coming every spring or 

 summer ; the locust of our climate septem-decennial, appear- 

 ing once in seventeen years ; but the cotton-fly has no regular 



