twenty-five per cent. According to this writer, the disease known to 
hop-growers as “honey dew” and “black blight” are caused by this 
Aphis. As the young lice attach themselves to the under side of the 
leaves, and as is the custom of the insects of this family, pump the 
juices so rapidly as to more than supply their wants, the overplus ex¬ 
udes from the honey-tubes and drops on the upper surface of the 
leaves below them, thus readily accounting for the presence of the 
honey-dew. This deposit of honey-dew, being subject to the action of 
the atmosphere and alternately moistened by the dews at night and 
dried by the sun during the day, is decomposed and changed from a 
transparent fluid to a black substance resembling soot, on which ac¬ 
count the term “black blight” is applied to it. 
It has been supposed by many observers that dry weather favors 
their increase, while wet weather retards it, and both Fitcbqand Harris 
favor this idea as applied generally to plant-lice. My own observa¬ 
tions do not wholly agree with this opinion, as I find that dry sea¬ 
sons appear to favor the increase of some species while others appear 
to be more abundant during hot moist seasons. Heavy rains, as a 
matter of course, are unfavorable to all kinds, but there is a difference 
in the effect of moisture and of heat on different species. Dr. Fitch 
quotes a paper read by F. W. Dogget, Esq.: “Upon the Weather in 
connection with Aphis Blight and the growth of Hops,” before the 
London Meteorological Society, in 1854, in which he says that “the 
years in which an excess of rain had fallen in or about the three 
months ending in September of therprevious year—the three follow¬ 
ing months and the March following being both comparatively defi¬ 
cient in rain—were followed by a short crop of hops, arising from 
the Aphis blight; and on the contrary, when the quarter ending in 
September of the previous year had been dry, an average or large 
crop had been grown. And when the quarter ending in September 
had been wet, and the December quarter very wet, a like result had 
followed.” 
But following this comes this very important statement: “This 
however was found to be modified by the temperature. When the 
weather of the previous year has been such as to indicate a blight, 
there may be a partial recovery if the temperature succeeding should 
be hot—with few exceptions, all the small crops were grown in years 
■ in which the temperature of the three summer months was below the 
average, and tne large crops were produced in those in which the temperature 
of like period was high.” I think it is apparent from these facts that 
in this case these differences are owing chiefly to the condition of 
the leaves; if the season is hot and dry the leaves are less succulent, 
and unfavorable to an increase of the Aphides, but when the condi¬ 
tions are such as to render them succulent the insect will increase. 
The operations of this species are very briefly and clearly described 
thus by an old author: “The progress and usual termination of the 
aphis blight may be thus described. The flies on their first arrival, 
immediately suck the underside of the upper small leaves of the vine 
(stem) and thus they deposit their young, upon the most succulent 
part of the plant. The multiplication of the lice is so rapid, that the 
leaves become so thickly covered as scarcely to allow a pin to be 
thrust between them. They quickly abstract the juices of the bine, 
so that the leaves assume a sickly brown hue, and curl up, and the 
