PEEIODICAL CICADA. 131 



of the Edwards river to its entrance into the Mississippi, nearly oppo- 

 site tlie mouth of the Iowa river, which was the place of begiiiuiug. 



The only gap in this outline, of any considerable extent, that I have 

 heard of, is the one above referred to, between the Sangamon river on 

 the south, and the Mackinaw river in Tazewell county, on the north — 

 the average course of this last named river being about on a line with 

 the southern point of Peoria county, and the intervening space embra- 

 cing the whole of Mason county. This gap is the more remarkable at 

 first sight, inasmuch as the bluffs on both sides of the Illinois river are 

 well wooded, and would, therefore, seem to form a natural continuation 

 of the locust range. The first explanation that occurred to me of this 

 break in the line, was in the sandy nature of the soil in this locality. 

 ♦ Mr. J. Cochrane, of Havana, Mason county, in his communications to 

 me upon this subject, speaks of the sandy character of the soil, and sub- 

 sequently, Mr. Stephen Tompkins, of Avon, Fulton county, who is an 

 old resident of this county, and who has often traversed it in all direc- 

 tions, described to me more particularly the character of this section. 

 He stated that from the southern point of Peoria county to Beardstown, 

 six miles below the mouth of the Sangamon river, the soil is very sandy 

 on the east side of the Illinois river, but less so on the west side. At 

 Beardstown the soil changes, becoming more intermixed with loam, 

 and it is a curious fact that a few locusts were seen at this place, though 

 it lies somewhat below the locust line. The supposition was that the 

 locust grubs do not find, in this sandy soil, the kind of subterranean 

 vegetation upon which it is their nature to subsist. But the correctness 

 of this explanation was disproved by subsequent correspondence with 

 Mr. Cochrane, in which he stated that there was an abundant brood of 

 locusts in Mason county a number of years ago, about the year 1859 

 or 1860 — as nearly as he can recollect — and that the groves and thickets 

 of what is known as the black-jack oak, were, in particular, badly cut up 

 by them. Mr. Tompkins also spoke of a visitation of locusts in Fulton 

 county, about ten years ago. Both these gentlemen, undoubtedly, refer 

 to the brood of 1861. The records show that there was a brood of 

 locusts in this year, which occupied a narrow strip of country, including 

 the northern border of Missouri and the southern border of Iowa, and 

 extending across the middle of the State of Illinois, in the line of 

 McDonough, Fulton, Mason, and Champaign counties. So that it 

 would seem that the true explanation of the absence of locusts in Mason 

 county in the year 1871, is the pre-occupati©n of this territory by 

 another and perhaps older brood. 



