142 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



According to Mr. Taylor's account, as given in the Smithsonian Re- 

 port for 1858, New Mexico was overrun by them in 1855 ; but so far we 

 have been unable to procure any data by which to verify this statement j 

 on the contrary, all the facts ascertained seem to contradict it. State- 

 ments have been made in reference to their migrations down the Eio 

 Grande to the vicinity of the Hornado del Muerto, while on the con- 

 trary it is asserted they have never been seen at Santa ¥6. Both of 

 these are doubtless incorrect. 



We have no positive evidence in reference to the locusts in Arizona 

 further than that they have been seen in the neighborhood of Saint 

 George, Utah 5 but the negative evidence indicates pretty clearly that, 

 with the exception of the northern border, this territory is not subject to 

 the visitations of the Eocky Mountain locust. 



We may therefore give the boundary so far as now known, about as fol- 

 lows: From Eagle Pass, Texas, to Santa Fe, N. Mex., thence west along 

 the 36th parallel of latitude to Southeastern Nevada. 



SUBPERMANENT REaiON. 



East of the mountains, between what we have described in the pre- 

 ceding chapter as the "Permanent Breeding Grounds," and the more 

 eastern section or temporary region which is visited only'at irregular 

 periods, is an irregular and not easily defined area, which forms a kind 

 of debatable ground, which cannot be distinctly classed with either of 

 these regions. As will be seen by reference to the chapter on migra- 

 tions, the movements in the sections north of Nebraska and Iowa do not 

 appear to be so regular as those of these States and the area south of 

 them. In other words, as we move northward the characteristic dis- 

 tinctions by which we are enabled to define the permanent breeding 

 grounds and area periodically visited gradually fade away, and we enter 

 an area where, although apparently not in their native habitats, the 

 Iqcusts appear more at home than farther south and southeast, L e., they 

 appear to be able to continue with considerable vigor for two, three, or 

 four years in succession. There are some reasons for believing that the 

 Coteau of the Missouri and the Coteau des Prairies have some influ- 

 ence in this matter, but the facts ascertained are not sufficient for us to 

 assert this with confidence. That the species is boreal in its habits and 

 characters is now admitted as beyond controversy 5 hence it is to be ex- 

 pected that as we move northward, where mountains are not necessary 

 to furnish the climatic conditions they require, the distinctions between 

 permanent breeding grounds and visited areas will be less marked. 

 This middle or subpermanent area is necessarily a shifting one, depend- 

 ing more or less upon the character of the seasons. Without attempt- 

 ing to give it any definite boundary, we may state that, so far as we 

 have been able to ascertain, these conditions are found in Western Mani- 

 toba, Eastern Dakota, Eastern Colorado, and Northwestern Nebraska. 



