228 
As the recorded facts indicate, within about ninety years there 
have been, in the Atlantic and Middle States, six periods of unusual 
abundance, namely, centering about the years 1799, 1817, !844-’45, 
1871-72, and 1876-78. These dates, which generally are inserted in 
larger type in the table, mark the time of culmination in the degree 
of abundance and extent of ravages committed, and were preceded 
by from one to several years of less or greater abundance. After 
the culmination, or year of greatest abundance, the fly often sud¬ 
denly disappears. This sudden disappearance is, without doubt, due 
to the great increase in the number of parasites, while the original 
increase is probably due to a succession of warm, damp seasons, 
favorable to the multiplication of the Hies. These seasons, when we 
look at the later Hessian-fly years, such as 1844-55, 1871-72 and 
1876-78, when the insect has become wide-spread over the western 
portion of the wheat area, were evidently areas of similar climatic 
features common to the Atlantic and Mississippi Valley States. 
Whether these seasons were warm and moist or not, we have not 
the means at hand to enable us to form an opinion. We simply at 
at this time draw attention to the greater desirability of putting on 
record the amount of correspondence between the meteorological 
conditions of the seasons of undue increase or unusual scarcity of 
insect pests, in order that we may be able in the future to make 
some calculations as to their probable increase or decrease that far¬ 
mers and gardeners may govern themselves accordingly. 
As stated to us by Mr. Thomas, in 1817, the rainfall from Maine 
to Maryland was slightly above the average, 1.01 per cent, of the 
mean. 
The winter of 1848-44 was the most severe in the West that had 
been experienced for twenty years; the spring was cold and late ; 
1844 was very wet over the West, in fact the wettest season known 
since its settlement, or at least since 1811. This was the year of 
the great flood in the Mississippi. It was also wet in parts of Vir¬ 
ginia and Maryland. But along the sea-coast from Maine to Flori¬ 
da the amount of rainfall was only about .90 per cent, of the mean. 
In 1845 it was not very wet in any section where wheat was culti¬ 
vated, the amount along the sea-coast being placed at .95, and this 
was about the same in the Middle and Northwestern States, vary¬ 
ing from .83 to .91 per cent of the mean. 
We thus see that the Hessian-fly years, 1817 and 1844, were wet 
years, periods of more than the average rainfall. Of 1871 we have 
no records at hand; the spring and summer of 1877 were damp and 
wet, and, also, appear to have been warmer than the previous year. 
There thus appears to be a correlation between the seasons of 
greatest abundance of Hessian-flies and a greater degree of moisture, 
if not of heat. 
