DR. BURNETT'S PAPER. 113 



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 food. Bat let us suppose that the 

 egg does not survive the winter ; how does it happen that when the worm first makes 

 its appearance it is found on the very summits of the cotton instead of the lower 

 branch ? parts that it would reach the soonest if it proceeded from the ground upwards. 



The phalena mori, or silkworm, 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 

 iu 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 

 insects, 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 mulberry tree shall again 

 afford them food iu the spring, and in this manner they are perpetuated, 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 it 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 appearance. The grasshopper is annual, coming every spring or summer ; the 

 locust of our climate septem-decennial, appearing once in seventeen years; but the 

 cotton-fly nas no regular periods of return, showing that when it reaches our climate 

 it is by some casualty. 



In proposition third, I maintain that if the cotton-fly sojourned here during the 

 winter or winters, when it did appear at all it would do so simultaneously through 

 the whole cotton district, instead of which we see it progressing regularly from south 

 to north and from west to east. 



Such are the speculations that I have entertained concerning the cotton-worm, from 

 which I conclude that it originates in South America, and reaches us through Mexico, 

 and never can become a denizen of our soil. 



Dr. Gorhaui's article excited considerable interest. It was republished 

 in several prominent Southern journals, and elicited a number of an- 

 swers. We have been able to find no evidence, however, that the theory 

 was accepted at that time by any writer on the subject. 



Seven years later (March 17, 1853) a communication from Dr. W. I. 

 Burnett, entitled " The Cotton-worm of the Southern States," was read 

 before the Boston Society of Natural History.* In this communication 

 the theory of migrations was again proposed. In this instance the the- 

 orist evidently based his conclusions on a small amount of evidence, as 

 is shown by the first paragraph of the following quotation, and the state- 

 ment in the third paragraph that he had seen the insect only in the 

 larva state. We quote Dr. Burnett's paper entire : 



During the past winter I have been collecting materials for the history of that most 

 devastating of American insects, the cotton-worm. In this I have been aided and 

 favored by several intelligent Southern planters, whose severe losses from the ravages 

 of this animal have made them keenly ah' ve to many of its habits and modes of life. 

 Of these gentlemen, I am particularly indebted to Mr. Robert Chisolm, of Palmetto 

 Hall, Beaufort, S. C., an intelligent and extensive cotton planter, who has with much 

 care watched the economy of this insect during several of its later appearances. He 

 has sent me several communications, from which, together with an examination of the 



'Published in 1854, Proc. Boston Soc. Nat, Hist,, iv, p. 316. 



8 ci 



