VISIT TO COLORADO. 19 



ferent in the higher plateaus and parks. At altitudes of from 8,000 to 9,000 feefc above 

 the sea, the principal hatching occurred iu May, and was later in proportion as we as- 

 cended, until, in the places with an altitude of 12,000 to 13,000 feet, the insects are 

 still hatching. At such great heights the mature dead are often to be found in large 

 quantities under stones and other shelter, which they sought last fall when prema- 

 turely overtaken by winter, and their young are hopping about in great numbers. As 

 no agriculture is carried on in these parks and passes, no effort is made to destroy the 

 insects, 



THE LOCUST PROBLEM MORE COMPLICATED IN. COLORADO THAN IN THE LOWER MIS- 

 SISSIPPI VALLEY. 



It is in consequence of the above facts that the locust question becomes so compli- 

 cated in your State. Colorado combines within her limits the meteorological and cli- 

 matic features of a dozen States. In the Mississippi Valley country, there are laws 

 governing the Fall invasions from the northwest and the return migrations in summer 

 on which to predicate with tolerable assurance. This is more particularly true south 

 of the forty fourth parallel. Your most disastrous swarms also come from the north 

 and northwest, and the insects which hatch out on your plains east of the mountains 

 are largely governed by the same laws and instincts as those which hatch to the east ; 

 on acquiring wings they leave, and those that rise before the second week in July will 

 bear mostly to the north and northwest. This is more particularly the case south of 

 the divide. After the middle of July the rains increase and the winds are more vari- 

 able, prevailing, so far as I have yet ascertained, greatly from the east or south in the 

 morning, but stronger from west or northwest in the afternoon. Swarms are liable, 

 therefore, at almost any time after the middle of July, to swoop down from the i^arks 

 and plateaus west of the range upon the valleys and plains to the east. These remain 

 within your borders, or, if they pass beyond, bear southeastwardly toward Texas. 

 From what light the Commission so far possesses, it becomes more and more plain that 

 I have been correct in considering the species as boreal,* and in locating the breeding- 

 grounds of the more disastrous swarms, like that of last year, in the plains regions of 

 the extreme Northwest, where the summers are short and the winters long and severe, 

 I find the exodus of the winged insects from that portion of your State lying east of 

 the mountains less complete than in Kansas and Missouri, for instance, and of the 

 earlier matured individuals that have not left, some commenced ovipositing a week or 

 so since. The young from eggs laid thus early will prematurely hatch this summer or 

 Fall, and inevitably perish; just as those now hatching toward the snow-line will per- 

 ish before attaining maturity. The insect is single-brooded, and the tendency to pro- 

 duce two broods where the summers are too long, is as fatal to the perpetuation of the 

 species as the want of time to properly mature a single generation where the summers 

 are too short. Both extremes obtain within the limits of your State, as, also, the in- 

 termediate conditions in which the species can thrive permanently ; whereas in no 

 part of the Mississippi Valley south of the forty-fourth parallel, and, probably, some de- 

 grees farther north, can the species hold its own continuously, and, with few excep- 

 tions, it seldom remains a single year. 



PROSPECTIVE. 



"While the record in Colorado up to this time is so interesting, in comparison with 

 that in other States, the probabilities during the rest of the season more deeply interest 

 your people. "What are the prospects?" This is the question put to me on every 

 hand. The farmer who is just about harvesting his wheat is anxious to know whether 

 the chances are that it will be suddenly ruined by the winged pests, as it has been in 

 past years, or that it will be unmolested. 



* We have in former writings designated the species as subalpine, but the term here used in its 

 zoological sense is more strictly correct, implying that region, as the Saskatchewan and Lake Superior 

 areas, between the subarctic and north temperate. 



