CHARACTEE OF THE PERMANENT BREEDING-GROUNDS. 69 
come better acquainted with the deserts in Africa, so long and so vaguely confounded 
under the name of "the Desert of Sahara," it has been observed that in this conti- 
nent, towards the east, savannas and pastures are found situated in the midst of 
naked and desert tracts. 
The treeless areas, especially when elevated, are the ones the locusts 
appear to prefer, and where, as a general thing, we find their homes, one 
species preferring the more elevated, broken, and mountainous sections, 
while another selects the lower broad barren plains. 
The two parts of the Mediterranean subregion are briefly described 
by Wallace as follows : 
The northern section is almost wholly a region of mountains and elevated plateaus. 
On the west, Spain is mainly a table-land of more than 2,000 feet elevation, deeply 
penetrated by extensive valleys and rising into lofty mountain chains. Italy, Corsica, 
Sardinia, and Sicily are all very mountainous, and much of their surface considerably 
•elevated. Farther east we have all European Turkey and Greece, a mountain region, 
with a comparatively small extent of level plain. 
Asia Minor to the Caspian is also of a similar character. 
This is the district of Caloptenns italicm, in some part of which it is 
to be found every year in greater or less abundance and more or less mi- 
gratory. The exact limits of its permanent distribution, and whether it 
is essentially migratory within these limits, are facts which do not appear 
to have been satisfactorily ascertained by European entomologists. 
The character of this region presents, in many respects, a striking sim- 
ilarity to the home of the Eocky Mountain locust. Here is an elevated 
,region, consisting of mountain ranges and peaks rising to the height of 
.ten, twelve, and even fourteen thousand feet above the sea, with extensive 
intervening treeless plateaus elevated from four to six thousand feet 
above the sea. The broad mountain ranges have their sides gashed by 
uarrow valleys, whose slopes are usually treeless, and grassy at least on 
the lower portion. A lack of arboreal vegetation, except in the heavier 
mountain masses, is a marked characteristic. The mountain area is bor- 
dered on its eastern flank by a broad, treeless plain, reaching from the 
northern lake region of Brit ish America to Mexico and extending eastward 
to the Missouri, its western border having an average elevation of four 
thousand feet and sloping eastward at the rate of Ave to ten feet per mile. 
That these two districts, resembling each other so much in general 
character, should be the homes of two migratory locusts so closely allied 
ps to belong to the same genus cannot be accidental, but results from 
>ome law of Acridian life which has not yet been discovered. To attempt 
its solution would carry us back into the history of the climatic changes 
>f the country, the vexed question of specific evolution, and into an ex- 
imination of the more recent geological changes. 
, The native habitat of the migratory locust, P. migrator ins, as we have 
ilready seen, consists chiefly of more or less elevated grassy plains, usu- 
ally called steppes, resembling in some respects the treeless plains of the 
Vest : in other words, the great pasture lands of Western Asia and 
Eastern Europe, the ancient Scythian hive, and the present home of the 
