PHYSIOLOGY AND DISEASES OF VEGETABLES. 115 
It would also be well that some information should be 
given of other varieties, as a knowledge of them will lead to 
better information of the one under our more immediate con- 
sideration. 
That a proper knowledge of this class of insects is worthy 
of attainment by the cultivators of the earth, has been fully 
evinced this year, 1853, by the great destruction of property 
which has taken place. It is only by having a thorough 
knowledge of the natural history of any class of animals that 
man can bring them under his own control ; he can subdue 
the strongest quadruped, also the most stupendous of the fish 
mammalia, yet the minute aphis fly becomes his master, and 
beyond his power; and this does, in some measure, arise 
from his ignorance of their natural history. To cover his 
ignorance, small insects and fungi are termed blights, coming 
from they know not where, or when and whence they go. 
The aphis insect, of one variety or another, attacks most of 
the farm crops ; there is one, the aphis granarcs , is often seen 
on the wheat crop, the barley and oats, in the middle of July; 
this is a green insect, like the aphis humuli ; when these first 
settle on the ears of corn, they are winged, but in about five 
days the other unwinged ( apterous ) progeny make their ap- 
pearance, feeding on the chaff scales of the corn ; in this state 
they are of a brownish-green. This aphis granaria is subject 
to the attacks of a parasitic fly, as we are instructed by Mr. 
Curtis, in the Journal of the Agricultural Society. This 
attack is by an ichneumonides fly, and is named by Mr. 
Haliday, aphidius averts , the eggs of which are laid within the 
body of the apterous aphis, the belly of the insect having 
been pierced by the ovipositer of the female aphidii. Mr. 
Curtis describes another parasitic fly, named ephedius , which 
pierces and deposits an egg in the body of the aphis insect, 
but inserts its ovipositer into the back, where it deposits its 
egg to destroy the aphis. 
Thus nature has in a most wonderful way provided means 
of checking the ravages of this blighter of man’s fair pros- 
pect ; without some such checks, the ravages of these plagues 
to the farmer’s crops would be much more destructive than 
they now are. On the subject of these parasitic flies, I shall 
have occasion to make some further remarks relative to pro- 
viding an antidote against the excessive ravages of the aphis 
insect amongst the hops, which has been felt this year, 1853, 
in places, as virulently as ever it was, whole acres and districts 
being totally destroyed. 
We shall also see that nature has provided a devouring 
