PROBABLE COURSE OF DIFFUSION. 71 
the north in British America. The two, besides differing in the length 
of the wings, are sufficiently unlike in appearance to attract the 
attention of students of Hemiptera. 
RELATION OF THE INLAND AND SKACOAST SHORT-WINGED FORMS. 
I do not wish to be understood as claiming that the short- winged 
form of chinch bug found in Ohio is precisely the same form as that 
found along the seacoasts, but it seems to me that the inland form 
originating from this maritime short-winged element, instead of acquir- 
ing wings of normal length as it drifted away from the coast, has really 
moved in the other direction, and the wings have become still further 
aborted. 
It will be observed by the illustrations given of both the inland and 
maritime short-winged forms (see figs. 3 and 4), that in some of the 
former the wings have become so aborted as to become almost invisi- 
ble, while in the latter, though the wings are very much shortened, 
they are nevertheless very clearly to be observed. It would seem, then, 
that we might reasonably presume that the species was originally 
long- winged, but, living along the seashore, the winged individuals 
have either flown each year inland or else been blown into the sea to 
such an extent that a short-winged form has thus been evolved which 
was unable to migrate and not easily blown into the sea. In pushing- 
inland while the country was still inhabited by the aborigines another 
source of destruction would confront these insects in the annual recur- 
rence of fires whereby vast areas of country were burned over in 
autumn, winter, or early spring, and these must have destroyed very 
many of the hibernating insects, while such individuals as migrated to 
sections not so burned over would escape destruction. 
PROBABLE COURSE OF DIFFUSION. 
Let us suppose that the species originally worked its way northward 
from South America, or even Panama, along the lowlands between the 
more mountainous interior and the Gulf of Mexico until it readied 
Texas, with its vast areas of level country extending not only across 
the State itself, but northward into British America, and. generally 
speaking, with the exception of the Ozark Mountains in Missouri and 
Arkansas, eastward to the Appalachian system extending from Gape 
Gaspe, Quebec, Canada, to northern Alabama. This area is more or 
less covered with a grass flora that affords ample food for these insects 
and it would seem that there was here offered every incentive to migra- 
tion broadly to the northward and eastward, and at the same time 
there would be the Gulf coast along which those individuals which 
either could not or did not migrate inland could make their way as hail 
their progenitors along the coast in Mexico. (See lig. 17.) 
Now, it would appeal as though the short winged individuals, it' there 
were any such, would remain along the coast, while the long-winged 
