55 
amination shows that the bugs are on the increase, winter wheat, 
wherever it is possible to do so, should be substituted for spring 
wheat; and oats, as far as possible, for corn. 
The uncertainty in reference to temperature will, perhaps, always 
prevent us from predicting with certainty that a coming year will 
he marked by the appearance of these insects, but we may say with 
assurance, that a wet year will not be followed by a Chinch-bug 
year. Although this is not all we desire to know in this respect, it 
is, nevertheless, a very important fact and may be used to manifest 
advantage by our agriculturists. 
It is proper to remark at this point, that we have been speaking 
only of the rainfall over the whole area designated, and the general 
appearance of the Chinch-bug over the same area. 
That these insects have appeared even in injurious numbers in 
limited localities in intermediate years, or times different from those 
indicated as possible Chinch-bug years, is certainly true. But, if the 
theory advanced is correct when applied to the area designated, as 
a whole it will probably prove true when applied to more limited 
localities. That is to say, if the meteorological record of a given 
locality within this area for a long .series of years is examined, it 
will probably reveal the fact that there is a similiar periodicity in the 
rainfall, though possibly not septenary. If this is found to be true, 
then the farmers of that locality will have a guide by which to ro¬ 
tate their crops and to take precautionary measures. 
It therefore becomes important for each section to keep a record, 
at least of the rainfall; for this will he of advantage not only in 
counteracting the Chinch-bugs, but numerous other species, and if a 
periodicity is ascertained will enable the farmers to adapt their crops 
as far as possible to the wet or dry seasons. 
The relation of meteorological conditions to the appearance of the 
Hessian-fly has not been worked out thoroughly as yet; still, enough 
has been ascertained to indicate that as a general rule, though not 
without exceptions, it is most abundant in rather wet and moder¬ 
ately warm seasons. This is shown by examining on the chart the 
principal years of its appearance in Illinois, 1844, 1846, 1871, 1872, 
and 1877. 
Warmth appears to be the chief element in developing the Aphides 
or Plant-lice, some species being more favored by a humid atmos¬ 
phere, while others develop more rapidly in a dry season. 
The Cut-worms are developed more abundantly in such seasons as 
increase the Army-worms, which, in their normal habits, are but 
Cut-worms, massing in armies and migrating being really an abnor¬ 
mal condition in their history. 
Observation shows, as heretofore stated, that as a general rule 
those species which occasionally develop in such vast numbers require 
for this purpose two consecutive favorable seasons, though the char¬ 
acters of the seasons for the different species differ somewhat. That 
is to say, those which bring out one species are not the ones which 
bring out another. As examples of the correctness of this statement 
I have only to refer to the migratory locusts, the Chincli-bug, as 
heretofore shown, the Hessian-fly, the Army-worm, etc. 
The Locust and the Chinch-bug require the same kind of seasons, 
that is, two successive dry years, the latter warm as well as dry; 
