INSECT ENEMIES OF WHEAT 179 



direction, but purely in search of food. They generally 

 march for one day, however, in the direction begun. If 

 the vanguard does change its course, the new direction seems 

 to be communicated in some way to those in the rear, which 

 follow in wave-like form. There sometimes occurs the singular 

 spectacle of two schools crossing each other, the individuals 

 of each keeping to their own course. Some remarkable records 

 have been made of phenomena resulting from the encountering 

 of obstacles to the march. In Europe Dongingk claims to have 

 seen them cross the Dniester for over one German mile, and in 

 layers 7 or 8 inches thick. "In 1875, near Lane, Kansas, they 

 crossed the Pottawatomie Creek, which is about 4 rods wide, by 

 millions; while the Big and Little Blues, tributaries of the 

 Missouri, near Independence, the one about 100 feet wide at 

 its mouth and the other not so wide, were crossed at numerous 

 places by the moving armies, which would march down to the 

 water's edge and commence jumping in, one upon another, till 

 they would pontoon the stream, so as to effect a crossing. Two 

 of these mighty armies also met, one moving east and the other 

 west, on the river bluff, in the same locality, and each turning 

 their course north and down the bluff, and coming to a perpen- 

 dicular ledge of rock 25 to 30 feet high, passed over in a sheet 

 apparently 6 or 7 inches thick, and causing a roaring noise 

 similar to a cataract of water." 



Their unfledged existence terminates in about 7 weeks. During 

 this time, even without change of direction, they could not 

 travel over 30 miles. The swarms of winged insects will per- 

 haps cover over an average advance of 20 miles a day. They 

 spread most rapidly 4 or 5 days after they become winged, 

 when, with a strong and favorable wind, they may reach a maxi- 

 mum of from 200 to 300 miles a day, and 50 miles per hour. The 

 swarms generally move toward the south and southeast. This 

 locust is single-brooded, dies with the approach of cold weather, 

 and normally hibernates in the egg state. Other kinds of de- 

 structive locusts occur, as lesser migratory, non-migratory, red- 

 legged, California devastating, differential, two-striped, pel- 

 lucid, and American Acridium, but the damage occasioned by 

 these has never been comparable to that caused by the Rocky 

 Mountain species. 



i U. S. Dept. Agr., Div. of Entomol., Bui. 25, pp. 21-22. 



