GENERAL DEDUCTIONS RESPECTING FLIGHTS. 181 



the attempt to carry out this desire, if it existed, was certainly not 

 pursued with the same determination as in that year. In fact, the flights 

 during 1877 present phenomena not observed in any previous year. 



GENERAL DEDUCTIONS. 



The facts ascertained by the Commission, in reference to flights east 

 of the Rock}^ Mountains, together with previously recorded observations, 

 justify us in drawing the following conclusions. Some of these con- 

 clusions we are satisfied may now be considered as established rules ; 

 the rest are yet uncertain, and are given as what the data ascertained 

 seem to indicate as rules, but which more complete evidence may show 

 to be erroneous. 



1. That they seldom migrate except when the atmosphere is in motion ; 

 in other words, when there is some wind, and that they move with 

 the wind. The facts ascertained warrant us in giving this as a rule, 

 which has few or no exceptions. It is evident that they depend 

 almost wholly upon the wind to move them, using their wings to sus- 

 tain themselves in the air; usually turning their heads toward the 

 wind and drifting backward. When the wind is very slight, they usu- 

 ally turn their heads with the wind and aid with their wings in moving 

 onward. 



2. That as a very general rule the resulting broods in the Border 

 States and the plains east of the mountains move northward, immedi- 

 ately after acquiring wings, toward the regions from whence their progen- 

 itors came ; that south of Dakota and Minnesota this appears to be 

 almost invariably the direction of the early flights ; that in these (Da- 

 kota and Minnesota) and northward, where the insects acquire wings 

 later in the season, the direction of the earlier flights is not so uniform. 



3. That at the time they acquire wings south of Dakota, the direction 

 of the wind is usually toward the north or northwest ; yet not to such an 

 extent as to entirely govern or explain the locust movements ; hence 

 there are strong reasons for believing that there is some other cause for 

 this tendency to move northward at this time. 



4. That later in the season, after those in the more northern regions 

 have acquired wings, the direction of the flights is generally south- 

 ward ; the general direction of the wind at this time is also southward, 

 but is by no means uniform or constant. 



5. That so far as can be ascertained those swarms moving northward 

 in the early part of the flying season, which reach their native breeding- 

 grounds, do not again return to the visited area ; while those which do 

 not reach these, as a general rule, do return southward, often moving 

 back and forth a number of times in the northern section. 



6. That these latter swarms, although apparently at the mercy of the 

 winds, appear to confine their movements generally to the area overspread 

 by their progenitors of the previous year, not strictly, but in a broad 

 sense. 



