PROBABLE COURSE OF DIFFUSION. 16 
individuals would, at least more or less of tliem. migrate inland, and 
at least some of these, but far more of those unable to fly, would 
be annually destroyed by the prairie fires, thus eliminating whatever 
tendency there might be to perpetuate the brachypterous forms, and 
develop a fully winged more or less nomadic race which, as it slowly 
advanced inland, lost all vestige of its brachypterous ancestry, if such 
had existed.* 
On the other hand, we might expect the shore-inhabiting individuals 
to continue in their progress along the coast, the winged individuals 
continually migrating inland, leaving a mixture of the two forms to 
push forward to the east coast of Florida and northward along the 
Atlantic to Cape Breton. As soon as this migration had passed the 
southern terminus of the Alleghany Mountains the inland spread 
would, very largely at least, be restricted to the area lying between the 
eastern slope of these mountains and the coast, thus leaving the whole 
area to the west to be occupied by the northward tide of migration 
instead of that from the east. East of the Mississippi River and south 
of the Ohio Eiver the country is more heavily timbered and the prai- 
ries are lacking, so that forest fires would here take the place of prairie 
fires; but in the Southern States the woods are composed more largely 
of pine, and Dr. Lugger, in Minnesota, finds that the chinch bug does 
not invade the region on which only pine and other Conifene grow, but 
that the more southern counties of his State, which are well wooded 
with deciduous trees, are invaded. He also calls attention to the fact 
that before the country was settled by the whites these timbered lands 
were burned over frequently, probably annually, but now the wooded 
areas are confined to small tracts interspersed among the farms, and 
as these are not annually burned over they afford suitable shelters for 
the chinch bug during winter, and the grain fields of the farmer afford 
ample food during the summer, while on the prairies which are burned 
over such is not the case, t 
Along the eastern coast the chinch bug has never been especially 
destructive to the wheat crop north of North Carolina, where, accord- 
ing to Dr. Fitch, t the earliest depredations occurred in 1783, while 
Webster § states that it threatened total destruction to the grain in 
1785; but since that time the ravages have not been nearly as severe as 
farther west in the Mississippi River valley. Strangely, too, nowhere 
along the Atlautic coast do we find the short-winged form far inland 
until we reach New York and the Xew England States, and what is 
*Prof. H. A. Morgan, entomologist of the State experiment Station of Louisiana, 
writing me under date of May 30, 1898, states that he lias never found the brachyp- 
terous form of chinch hug in that State, and I did not observe a single individual 
of these among the many macropterons specimens taken l>> myself in that State. 
tFirst Annual Report of the Entomologist of the State Experiment station of the 
University of Minnesota, 1895, p. L'ti. 
t Second Keport on Noxious, Beneficial, and other Insects of New York, p. -7-. 
v> Wehster on Pestilenee, Vol. I, 279. 
