16 GENERAL ZOOLOGY 



which destroys them. Members of the swarm are then cap- 

 tured, dipped in the solution, and turned loose, thus spreading 

 the disease. The lesser locust has at various times caused con- 

 siderable damage to growing crops by appearing at different 

 points in the New England states. 



There are several species of migratory locusts in the Old 

 World whose visitations in the past have been most destruc- 

 tive, especially in Egypt, Palestine, Syria, Asia Minor, China, 

 France, Russia, and Germany. They have appeared in almost 

 incredible numbers in certain years, so that a swarm has been 

 estimated to cover two thousand square miles of territory. 

 The prophet Joel has described the onslaught of locusts in 

 the lines beginning, 



A day of darkness and of gloominess, a day of clouds and of thick dark- 

 ness, as the morning spread upon the mountains : a great people and a 

 strong; there hath not been ever the like, neither shall be any more after 

 it, even to the years of many generations. JOEL ir : 2. 



It is easy to appreciate the fact that in thickly settled areas 

 famine and pestilence may follow the visitation of these in- 

 sects. Out of the twelve hundred or fifteen hundred species 

 of locusts in the world, only about twelve have the habit of 

 migration to any great extent, and these are mostly species 

 which live on large, elevated, open tracts of desert or semi- 

 desert character, where the climate is dry and hot, for ex- 

 ample, such regions as the steppes about the Caspian Sea. 

 Perhaps the determining factor in the migration is exces- 

 sive multiplication and the consequent need for new feeding- 

 ground. 



Many locusts produce sounds by rubbing the inner edge 

 of the posterior femur against the outer edge of the first pair 

 of wings. It is supposed that this is done only by the males, 

 though it may be possible that the females produce sounds 

 which we are unable to hear. Some locusts produce a noise 

 in flight by the friction of the wings. 



