72 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
ing in the summer as low as 20 and seldom reaching CO, as will be 
seen by reference to the meteorological data furnished by Professor Abbe 
and fouud in our former report, aud to that found in a succeeding chapter. 
In studying carefully the climatic conditions of the various locust 
areas, we notice this difference between those in the Eastern Continent 
north of the equator and that of our species. The former have their 
greatest extension east aud west, and in the case of P. migratorius 
and C. italicus in the direction of the migrations, while that of C. spretus 
extends north and south, or at least presents its best-defined side toward 
the east and at an angle to the usual course of migrations. The area of 
A. percgrinum has its greatest extension east aud west, the western half 
at right angles to the usual course of migrations. In speaking of the 
character of the area occupied by this last-named species, we omitted to 
mention the elevated portion along the southern limits. 
As P. migratorius. has its chief, or, as we might say, central area about 
the Caucasus range, and a mountain home or back-ground appears 
essential to the migratory Calopteni, it is possible that this character- 
istic is more important to the development of locusts than has gener- 
ally been supposed. 
CHAPTER IV. 
HABITS OR CHARACTERISTICS OF LOCUSTS IN ALL COUN- 
TRIES WITHIN THEIR AREAS OF PERMANENT DISTRIBU- 
TION, SO FAR AS THESE RELATE TO THEIR MOVEMENTS. 
The chief items of importance under this topic are the following : First. 
Are they normally sedentary in the permanent area, developing under 
favorable climatic conditions in immense numbers and becoming migra- 
tory from some cause connected with this development ; or are they es- 
sentially migratory in character ? Second. Do they breed annually 
throughout this entire area, or only in certain portions, changing from 
time to time from one locality to another ? 
In our First Report, in the chapter on " Permanent Breeding Grounds," 
we expressed briefly our opinion on these points in reference to the Rocky 
Mountain locust, as follows : • 
It is not to be inferred that the locust breeds continuously over the whole extent 
of this area each year, as it is to be understood that the locust within its native, per- 
manent habitat is essentially migratory in its habits, and while for a series of years it 
may deposit its eggs in a given river valley, in some park, or in some favorable area 
on the plains lying about the mountain, in a certain year or for several years in suc- 
cession it may desert its customary breeding grounds for adjoining regions or cross a 
low range of mountains and breed in a more distant valley. Moreover, the true breed- 
ing grounds in this area are, for the most part, confined to the river bottoms or sunny 
slopes of uplands, or to the subalpine grassy areas among the mountains, rather than 
continuously over the more elevated, dry bleak plains. 
