80 ORTHOPTERA OF MINNESTOA. 



wings at the time of producing sound by vibrating them, in 

 fact almost the whole body vibrates — is a sort of sounding- 

 board. Both actions strengthen the sounds. We can do the 

 same thing if we vibrate the strings of a guitar and swing the 

 instrument in the air; in this manner we imitate the sounds 

 of bells, in other words, increase the sounds. It is also a well 

 known fact that the pitch of a sound depends upon the num- 

 ber of vibrations. Knowing the number of vibrations we 

 can judge from the sounds how many were made to produce 

 them. If, for instance, a fly produces during flight the sound 

 f'', it had to make 352 beats of the wings per second to do 

 so. If our honey-bee is active the sound a' is produced 

 during flight, or 440 beats per second ; if tired e' is produced* 

 or 336 beats per second. 



Some insects also produce sounds to communicate with 

 others of their kind. If we put some honey near the entrance 

 of a bee-hive some of the bees will soon discover it, and thev 

 immediately call others to this valuable Klondyke of honev 

 by producing the sounds a'', h'', or q."\ according to their 

 size. These sounds will invariably call many bees from the 

 hive, and the honey is soon stored away in safer quarters. 



ORTHOPTERA OF MINNESOTA. 



The members of this order are, almost without excep- 

 tion, injurious to agriculture, horticulture and forestry-, and 

 some of them have become a ver\' annoying pest in our 

 houses. When we listen during the warm nights of summer 

 to the songs of our arboreal Katydids, to the chirping 

 sounds of crickets, or to the shriller tones produced by 

 locusts and grasshoppers, we are apt to forget that insects 

 forming this order of insects belong to the most terrible 

 scourges known to man. The older inhabitants of our state 

 are not apt to forget, however, the devastations caused b\' 

 the great swarms of migratory locusts in the past, while 

 more recently farmers in various parts of the state had to 



