DESIGNATION OF " PERMANENT BREEDING-GEOUNDS." 57 
outer line, sliowiug tlie utmost extent of its presence in the condition of 
bands of winged insects beyond the region where the species may live 
and propagate, or, in other words, the extreme boundary of its flights. 
Our investigations, made independently of a knowledge of Koppen's 
conclusions, led to a somewhat similar result. We found it necessary, 
in order to express the relations of C. spretus to the various parts of the 
area over which it roams, to designate an inner or central region as its 
" permanent breeding- grounds," and an outer circumscribing belt as the 
"temporary region," corresponding with Koppen's first and second 
divisions. Its incapability of continuing its existence in this temporary 
region is so marked that we have attempted to designate an interme- 
diate area showing the limits of the oscillations of the permanent breed- 
ing-grounds. But this, in the opinion of the writer of this chapter, is 
too indefinite to be of any real value, an 'opinion which it is proper for 
me to state is not fully concurred in by all the members of the Commis- 
sion. Our investigations of this species have brought to light no facts 
to warrant us in designating an outer belt corresponding with Koppen's 
third area, as its flights do not extend into any sections, so far as ascer- 
tained, where it may not produce at least one resulting brood. 
It is necessary for us to call attention here to the fact that this ar- 
rangement does not include all of the relations of migratory species to 
the regions they are found inhabiting. For example, a species may not 
be essentially migratory and hence may be found to possess this char- 
acter in one district where the conditions are favorable whde in another 
section it may be truly sedentary. Such appears to be the case with A. 
americanum, which in the southern half of the United States is sedentary, 
while in Yucatan and other parts of Central America it is said to be 
migratory. If P. cinerascens is ever truly migratory, of which we have 
some doubt notwithstanding the affirmative evidence on this point, then 
it forms a second example, as we are informed by Selys-Longchamps 
that it is sedentary iu Belgium and other parts of Europe. 153 How far 
this characteristic applies to other locusts of the Eastern Continent we 
are unable to state, as the attention of European entomologists does not 
appear to have been specially directed to this point. 
As will be seen hereafter, the evidence obtained by the Commission 
in reference to our Bocky Mountain locust shows it to be essentially 
migratory. The same also appears to be true of A. peregrinum and P. 
migratorius. 
We may as well remark here, in order that our arguments and con- 
clusions may be the better understood, that we do not include in the 
category of " migratory locusts" or of " locusts " in the true sense, those 
Acridians which occasionally, through the influence of climatic condi- 
tions, are greatly developed and even induced to migrate for short dis- 
tances. 
As the native home of an essentially migratory species must be a 
'"Compt. Bend. Soc. Ent. Belg., 1871-2, xxiv. 
