54 
1 am fully aware of the fact that a longer series of rainfall records 
may serve to show that the conclusion arrived at here in reference 
to the septenary cycles is erroneous, hut we can only base our 
arguments trpon such facts as are known; we are, therefore, justi¬ 
fied in relying upon this conclusion until it is shown to be incor¬ 
rect. We must again call the attention of the reader to the fact, 
that it is limited strictly to the area designated, as it is not claimed 
that it is true in reference to any other section, though possibly it 
may be. 
Assuming it to be sufficiently established to justify us in attempt¬ 
ing to use it practically in economic entomology, let us see how 
this is to be done. 
The first and very important practical fact revealed is that we 
may expect at most but two Chinch-bug years in every seven, with 
the strong probability, amounting almost to a certainty, that there 
will not be two in succession. As heretofore stated, two successive 
dry years are necessary in order to develop this species in excessive 
numbers; the rainfall records seldom show three dry years in suc¬ 
cession, hence the Chinch-bugs are not likely to appear in injurious 
numbers in two successive years. The years 1854 and 1855 may, 
perhaps, form an exception to this rule. It is possible that the 
second brood of the first year may be sufficient to excite alarm, but 
experience has shown that they do but little injury. We may, per¬ 
haps, with safety assume, as a general rule subject to occasional 
exceptions, that they will not appear more than once in excessive 
numbers during any of the septenary periods. 
If the facts shown in reference to periodicity in our rainfall are 
confirmed by future investigations, and this periodicity shown to be 
a meteorological law of the area indicated, the practical advantage 
of this knowledge to our farmers is apparent to every one. By this 
knowledge they will be enabled to predict with a reasonable degree 
of certainty when to expect these insects, and can rotate their crops 
so as to suffer the least possible injury. This knowledge will also 
enable them to dispense with precautionary measures except in such 
years as are likely to be followed by the appearance of the bugs. 
Experience has shown, and farmers are now becoming fully aware 
of the fact, that spring wheat and corn are the crops that chiefly 
aid in sustaining and developing this pest. Why corn should aid in 
this respect is easily seen, as it is the only extensive crop on which 
the second brood can feed. But why spring wheat should aid more 
in developing them than winter wheat is not so easily explained, but 
that such is the fact must be admitted. It may possibly be ac¬ 
counted for on the presumption that the climate of the spring wheat 
region is more congenial to them than that of the winter wheat 
area. 
These facts, combined with a knowledge of the time when the dry 
seasons are to be expected, will enable the farmers to substitute 
other crops as far as possible in place of spring wheat and corn. Even 
if the conclusion in reference to periodicity in rainfall should prove 
erroneous, the fact that two successive dry years are necessary to 
develop this species in excessive numbers will suffice to give notice 
at least one season in advance and allow the farmers to adapt their 
crops to the circumstances. When a dry season comes and an ex- 
