On the American Locust. 183 



Dr. Jones was informed, that the locusts have been 

 found at the depth of twenty feet under the ground. 

 In some parts of New-Jersey, they have been found at 

 the depth of seventeen or eighteen feet. But, in general, 

 they do not penetrate so deep. They are often seen 

 ten feet below the surface. I have supposed, that they 

 generally penetrate lower in the northern than in the sou- 

 thern parts of our continent ; but many facts must be 

 collected before this point can be fully determined. 



It is certain, that the depth to which they penetrate is 

 much influenced by the soil of the district in which 

 they make their appearance. In many parts of Mary- 

 land, Virginia, &c, it would be impossible for the 

 whole of those which do enter the ground to penetrate 

 to the depth of even six or eight feet ; owing to the su- 

 perficial position of the calcareous strata, which extend 

 for miles, in succession, through the country. 



Fourteen years is said to be the interval between the 

 periodical returns of the locust. I believe seventeen 

 years is the more regular period. Within my own re- 

 membrance, the interval has been exactly seventeen 

 years, in Pennsylvania and New-Jersey, in the same 

 districts of each of these States. In New Jersey, about 

 Elizabeth- Town, &c, they made their appearance, in 

 very great numbers, in the latter end of May, 1792. 

 Previously to this, they had appeared, in the same 

 neighbourhood, three different times, within the re- 

 membrance of some of the oldest of the inhabitants ; and 

 the intervals between their returns had been exactly se- 

 venteen years. Linnaeus seems to have been well in- 



