CHARACTER OF DIFFERENT FLIGHTS. 143 



CHAPTER VII. 



MIGRATIONS. 



The locusts are the only insects which may be properly termed mi- 

 gratory. It is known that certain butteriBlies pass in swarms from one 

 place to another, but such flights are local. Swarms of Banaits arcMp- 

 pus, a common butterfly, have been seen in the Mississippi Yalley either 

 in the spring or autumn, but not flying long distances. In the Old 

 World the migratory locust is known to fly for a distance of four or five 

 hundred miles into central Europe from its permanent breeding- a.rea in 

 Asia. The flights taken by locusts in North America may extend over 

 a distance of between one and two thousand miles, from their native 

 breediug-x)laces in Montana, for example, to Kansas andMissouri, and per- 

 haiDS Texas. As a rule the flight is undertaken only during a part of the 

 day, and in fair, clear weather, so that the desire for food, cloudy, rainy 

 weather, and adverse winds may keep them from rising and taking 

 wing. In a favorable day they rise early in the forenoon, from eight to 

 ten o'clock, and settle down to eat by four or five in the afternoon. The 

 rate at which they travel is variously estimated from three to fifteen or 

 twenty miles an hour, determined by the velocity of the wind. Thus 

 insects which begin to fly in Montana by the middle of July may not 

 reach Missouri until August or early September, a period of about six 

 weeks elapsing before they reach their destined breeding-grounds. 



In order to avoid circumlocution in speaking of the various kinds of 

 flights of the Eocky Mountain locust, the Commission has been com- 

 pelled to adopt certain terms by which to designate them. 



Invading sicarms. — This term, when used in reference to their move- 

 ments east of the mountains, applies to those swarms or hordes which 

 move down from their native hatching-grounds in the West and North- 

 west, into those sections where they are not permanent residents. It is 

 only applied to those hatched in their native habitats, and not to those 

 swarms which having hatched in the visited area move northward or 

 northwest and then return, as is often the case. 



Returning swanns. — This term is used to designate those swarms 

 which, having hatched in the invaded district where they are not per- 

 manent residents, and having acquired wings, led, apparently by some 

 natural instinct, return to their native home in the Northwest and West. 



Local flights. — This is a term used to designate the movements of 

 those hatched in the invaded district, to and fro, from point to point in 

 that district. It is not so accurate and definite in its application as the 

 other terms mentioned, as it is applied to those movements to the north 

 and northwest, no matter how general they may be, if the swarms ap- 

 pear to fail in their efforts to reach their native home. But not with- 



