176 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



ward movements in 1877, after the 10th of July, nearly equaled in extent 

 the northward movements prior to that date. 



MOVEMENTS IN DIFFERENT DIRECTIONS AT THE SAME TIME. 



These are of two kinds — contrary movements over large areas on the 

 same day, and flights in different directions at the same time and place. 



It will be seen by inspecting the records given in Appendix No. 13, 

 and even that of the two days heretofore given, that it is no uncommon 

 thing for flights on the same day to vary at different points from north- 

 east and north round westward even to southwest, and likewise in the 

 southward flights from southwest and south around to east. Hence we 

 have throughout considered all movements northeast and around the 

 northwest quarter of the compass to west as northward movements, 

 and those around the southeast quarter of the compass as southward 

 flights. Movements in these opposite general directions on the same 

 day are not so common, yet so far as single points of observation are 

 concerned they are not infrequent, and in several instances occurred in 

 the same or adjoining counties. 



Professor Whitman states that on the 1st of July reports from forty- 

 one points give flights in nine different directions. As a rule, these 

 variable flights occur on warm, still days, when there is no general 

 movement of the air in any one direction. 



There were a few days in 1877 in which there were movements in dif- 

 ferent directions over large areas. For example, on the 5th of July, 

 locusts were flying north, northwest, and west (or northward) in South- 

 western Iowa, Southwestern Minnesota, and Eastern Dakota, and south- 

 ward or southeast over a broad belt running northwest and southeast 

 through the middle of Minnesota. The 2d of August furnishes an instance 

 of three difierent currents, two southeast and one northwest. In South- 

 eastern Dakota and as far east into Minnesota as Nobles County, the 

 movement was to the northwest. Through the central parts of Minne- 

 sota and Northwestern Iowa the flights were southward ; in Nebraskii 

 and Kansas the movement was chiefly to the southwest. At some of 

 the points in Minnesota the flights in opposite directions were quite 

 heavy; in Nebraska tbey were light and irregular. As a matter of 

 course, the direction of these movements depended entirely upon the 

 direction of the wind, and it would scarcely be worth while to mention 

 them were it not for the bearing they have upon the question of the 

 " return flights.'^ 



Flights in opposite directions at the same time and place were not of 

 frequent occurrence, but were occasionally observed. They were always 

 one above the other, and doubtless in different currents of air; some- 

 times in directly opposite directions, sometimes one column crossing 

 the other obliquely. Those heretofore alluded to as having been ob- 

 served by Professor Aughey were moving in almost precisely opposite 

 directions, one northward and the other southward, on July 20, 21, 25, 

 and 26, at Dakota City, Nebr.; also, between Yankton and Sioux City 



