30 



" The locust is quite or nearly as destructive in Africa, Asia, and Southern Europe, 

 as in this country, but the laws of their migrations and their connection with meteorolog- 

 ical phenomena have never been studied in those regions, and it remains for the United 

 States, with its Weather Signal Bureau, to institute in connection with the scientific sur- 

 veys of the West investigations regarding the nature of the evil, and the best means to 

 overcome it. 



" In endeavouring to trace the connection between the migrations of the locusts and 

 the course of the winds at different months, the writer has been led into some theoretical 

 considerations which seem to be supported by the facts presented in the unpublished re- 

 port, and which may be confirmed or disproved by future investigations. 



'^ History of the Mir/rations of the Locust. — The following table, compiled from the 

 reports of A. S. Taylor," the late iMr. B. D. Walsh, Prof. C. V. Kiley, Prof C. Thomas, 

 Mr. G. M. Dawson, and the observations of Mr. W. N. Byers, will show the years when 

 the locust was excessively abundant and destrirctive in the different territories and states, 

 and also serve to roughly indicate the frequency and e.xtent of the migrations of the de- 

 structive locust of the West. The dates which are starred are years when the progeny of 

 the locusts of the preceding year abounded, and when in most cases there were no fresh in- 

 cursions from the westward. The species referred to under the head of California, Wash- 

 ington and Oregon may be some other than Ccdoptenus spretus. 



" This table and the data on which it is based are necessarily very imperfect, owing 

 to the vast extent of the territory over which the locusts ^warmed, and the fact that the 

 greater portion is uninhabited, while the inhabited portions have been settled only within 

 comparatively few years. 



"The Theory of Migrations.— (\) The immediate came of the miyrution of the locust 

 from its origitud breeding plates is the unusual abundance of tlie species during certain years. 

 It has been found in some cases that the exceptional years when the locust mi»rates are 

 periods of unusual heat and dryness, conditions unusually favourable to the excessive 

 increase of insect life. As may be seen in the accounts of the eastern locust the "rass 

 army worm, the grain ajAis, the chinch bug, and other less destructive insects,' when the 

 early part of the season, the spring and early weeks of the summer, are warm and dry, 

 without sudden changes of temperature, insects abound and enormously exceed their 

 ordinary numbers. When two such seasons occur, one after the other, the conditions 

 become still more favourable for the undue development of insect life. Now it is well 

 known that in the Eastern States the summers of 1860 and 1874, preceding the appear- 



