COMPARISON WITH THE LAWS OF GEOGRAPHICAL ZOOLOGY. 65 
The universal testimony of those who have witnessed the locust mi- 
grations in Algiers, Morocco, and other portions of [Northern Africa 
along the Mediterranean shore (exclusive of Egypt) is that they always 
come from the south. As proof of this, we have only to refer the reader 
to the accounts we have given relating to this section. 
In addition to this, the testimony of the French naturalists and recent 
authorities show beyond dispute that the locust of this region is A. pere- 
grinum. What species are found on the plains of Australia and South- 
ern Africa is yet a matter of doubt, but the facts given are sufficient to 
show that the great intermediate tropical belt is not infested by P. migra- 
torius as a migratory species. 
Before proceeding further in the discussion of this subject, let us see if 
our conclusions will accord more nearly with the laws of geographical 
zoology than the theory attributed to Koppen. If so, then it is fair to 
presume that we are nearer the correct solution of this question than he is. 
If the reader will take the trouble to examine Wallace's map of his 
Nearctic Eegion 168 and compare the Eocky Mountain subregion (No. 2) 
with the line marking the permanent distribution of C. spretus on our 
map he cannot fail to observe the almost exact coincidence of the 
boundaries of the two, the only difference worthy of notice being the south- 
ern extension, which, in reference to C. spretus, is yet an open question. Is 
this purely accidental ; or is it in accordance with the laws of animal 
distribution which have enabled the talented author of that work thus 
to map the boundaries of the faunal region ? 
Let him now turn to the map of the Palearctic Eegion, 169 . Although 
he will fail to find such exact coincidence between the limits of locust 
distribution and the boundaries of the faunal districts as marked by the 
author, yet a careful examination will show that each migratory locust 
is, after all, confined, as far as its area of permanent distribution is con- 
cerned, to its own faunal district. The reader will observe that in the 
southeast part of subregion 1 (European) and the southwest of No. 3 
(Siberian) there is an immense area marked as pasture-land, which ex- 
tends east and west from Hungary to China, embracing within its bounds 
all that section to which the name Tartary, or Tahtary, was applied by 
the early writers and travelers. The northern boundary of this area, as 
mapped by Wallace, corresponds almost exactly with the line of perma- 
nent distribution of P. migratorius as given by Koppen ; and we are 
inclined to believe that, with the exception of the debatable ground of 
Asia Minor and Syria (or Asiatic Turkey), the southern and eastern 
limits represent approximately the southern and eastern boundary of 
permanent distribution of this species. 
From these broad, grassy plains, or steppes, carried by easterly winds, 
they sweep over Southern and Central Europe, usually along the northern 
shore of the Black Sea, but occasionally from Asia Minor ; the Ukraine 
and the region of the Crimea, occupying the straits or narrows of this 
""Geographical Distribution of Animals, I. p. 115. "»Vol. L., p. 181. 
5l 
