574 
DIPTERA. 
of the leaf.” His remarks in Professor Silliman’s Journal 
are to the same effect. Other authorities on this point 
might be mentioned; but the foregoing are sufficient, in 
my opinion, to establish the fact, that the Hessian fly lays 
her eggs on the leaves of wheat soon after the plants are up. 
“ The number on a single leaf,” says Mr. Herrick, “ is often 
twenty or thirty, and sometimes much greater. In these 
cases many of the larvae must perish. The egg is about a 
fiftieth of an inch long, and four thousandths of an inch in 
diameter, cylindrical, translucent, and of a pale red color. 
Mr. Tilghman was correct in supposing that the eggs would 
hatch in less than fifteen days, under favorable circum¬ 
stances ; for, if the weather be warm, they commonly hatch 
in four days after they are laid. 
The maggots (Fig. 258, natural size), when they first 
come out of the shells, are of a pale red color. 
Forthwith they crawl down the leaf, and work 
their way between it and the main stalk, passing 
downwards till they come to a joint, just above 
which they remain, a little below the surface of 
the ground, with the head towards the root of 
the plant. Having thus fixed themselves upon 
the stalk, they become stationary, and never 
move from the place till their transformations 
are completed. They do not eat the stalk, 
neither do they penetrate within it, as some, persons have 
supposed, but they lie lengthwise upon its surface, cov¬ 
ered by the lower part of the leaves, and are nourished 
wholly by the sap, which they appear to take by suction. 
They soon lose their reddish color, turn j)ale, and will 
be found to be clouded with whitish spots ; and through 
their transj)arent skins a greenish stripe may be seen in 
the middle of their bodies. As they increase in size, and 
grow plump and firm, they become imbedded in the side 
of the stem, by the pressure of their bodies upon the 
growing plant. One maggot thus placed seldom destroys 
Fig. 258. 
