162 EEPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



RETURN MIGRATIONS EAST OF THK ROCKY MOUNTAINS IN 1877 OF THE 

 LOCUSTS HATCHED FROM EGGS LAID THE PREVIOUS AUTUMN. 



The facts here stated and the records of flights found in the appen- 

 dix show clearly that in the region south of Minnesota the locusts, as 

 soon as they acquire wings, are disposed from some cause to move north- 

 ward. From the time they commenced to fly at Bastrop, Tex., April 

 19, until the 8th of July, when a swarm was observed at Glencoe, Nebr., 

 moving south, the direction of the flights was, with very few exceptions, 

 northward, varying in a few cases to westward. In Minnesota the case 

 was different, although there were long flights in June to the northwest, 

 jet the rule can scarcely be said to apply here, for the exceptions are too 

 numerous. From the facts heretofore ascertained in reference to their 

 habits this movement was anticipated and predicted. The movements 

 in previous years had already led to the conclusion that by some law 

 governing them there is a tendency in the resulting broods hatched in 

 this visited area to return to the native habitats from which their pro- 

 genitors came. That the broods of 1875 and 1876 hatched in the area 

 south of Minnesota, did move in this direction is conclusively shown by 

 the data furnished in Mr. Eiley's reports for 1875 and 1876, and in the 

 papers on locusts by Messrs. Dawson and Whitman. 



As will be seen by examining our circular No. 1, a copy of which will 

 he found on p. 3 in this report, our first and second questions related 

 to the flights of locusts and the direction of the wind at the time 

 These questions have been more generally answered than perhaps any 

 ■others in the circular, and enable us to give more fully than has ever 

 before been done the movements of locusts east of the Rocky Mountains, 

 and especially in the invaded section, which we have designated the 

 ** temporary breeding-grounds.'' 



The past season has been an unusually favorable one fo-r studying 

 the *' local flights " or limited migrations, from the fact that these have 

 occurred to an extent hitherto unknown in these border States and ad- 

 jacent Territories. The amount of material collected for the purpose of 

 solving the various problems connected with these flights is very large, 

 and although it may not suffice to dispel all the mystery connected with 

 them it has enabled us to explain much that has hitherto been a matter 

 of doubt and uncertainty, and to lay down the general laws which gov- 

 -ern them. 



Strange as it may seem to those who have not carefully studied the 

 characteristics and habits of the species, yet it is true that it is possible 

 in almost every instance to distinguish an invading from a local swarm 

 although moving in the same direction and apparently from the same 

 point. Those who have had considerable experience with them are 

 generally able, from an inspection of the insects alone, to decide with 

 reasonable certainty this point. But there are other and still more im- 

 portant methods of determining it. 



