LOCUSTS AND GRASSHOPPERS (ACRIDIID^E}. 123 



As a rule, the individuals who first acquire wings do 

 not leave the general swarm, but remain with it until 

 they all are mature, when the whole body will take wing 

 together. In cases, however, where great swarms of 

 different ages are mixed, the adults will suddenly arise 

 and be off, northward, leaving their companions, the 

 " Voetgangers," to trudge along behind until such time 

 as they can follow. 



By the middle of summer usually, the young have 

 their wings, when they invariably all take flight and 

 speedily disappear, travelling north, not a single specimen 

 remaining behind in the Colony. 



Distance to which Swarms may Migrate. 



In the Old World the migratory locust is known 

 to travel a distance of four hundred or five hundred 

 miles into Central Europe from its permanent breeding- 

 area in Asia ; in North America the distance to which 

 swarms may migrate in the course of a season may 

 extend over a thousand miles. 



The space over which a single flight may extend is 

 not definitely known, but that it is considerable is certain. 

 As the locusts rely chiefly upon the wind to bear them 

 along, it depends upon the rate at which the wind moves, 

 and the length of time they can remain in the air 



