186 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



zoogeograpbical province of Xorth America, not occurring in the Pacific 

 province or in the eastern or Atlantic provinces, except in the latter 

 periodically. 



SUPERMANENT REGION. 



II. The region in which the locust breeds less permanently, bat is 

 liable to be invaded each year when it multiplies in excessive numbtTs 

 in its truly permanent breeding or hatching grounds, lies immediately 

 east of the 104th or 105th meridians, on the elevated plains east of the 

 Rocky Mountains. The altitude of this area constantly diminishes east- 

 ward until in elevation and the character and contour of the soil it fades 

 into the region intermediate between the plains and the prairies of the 

 western edge of the Mississippi Valley. 



The eastern limits extend north of the 45th parallel to the 97th 

 meridian approximately. From Fort Eausom, on the Cheyenne River, 

 the line demarking the eastern limits curve southward and westward to 

 Pueblo City, Colo. This region includes a large portion of British Amer- 

 ica between the United States boundary line and latitude 53^ north, and 

 between the 97th and 104th or 105th meridians. It includes nearly all 

 of Dakota, the western third of l^ebraska (now mostly unsettled), the 

 extreme northwest corner of Kansas, and comprises the northern half 

 of Colorado, east of the Rocky Mountains. 



Between the permanent and subpermanent breeding area there are no 

 natural barriers, one region shading imperceptibly into the other, the 

 limits between them being arbitrarily drawn. 



TEMPORARY REGION. 



III. This region is represented on the map by the dotted area east 

 of the great plains. South of the 42d parallel, and west of the limits of 

 the subpermanent breeding grounds, the region is nearly correct ; but in 

 Wyoming, Idaho, and Montana the limits are only approximately given, 

 and are liable to future correction. 



CHAPTER VI. 



GEOGRAPHICAL DISTRIBUTION 



As the preceding chapter, on the " native breeding grounds," contains 

 as complete a statement of the nature and extent of these as we are 

 able to give from our present information, and the chapter on " migra- 

 tions " contains a somewhat full account of the movements of the swarms 

 within the area overrun by them, we shall devote this chapter simi)ly to 

 tracing the extreme limits of the migrations, or, in other words, the 

 bounds of the locust- visited area, and to an explanation of what we term 

 the " subpermanent region." 



