Vot. LIX. No. 2639. NEW YORK, AUGUST 25, 1900. 
THE DESTRUCTIVE HESSIAN FLY. 
IT8 LIFE HISTORY AND HABITS. 
What Can Be Done With It? 
In early May we had in this locality what appeared to 
be a fine prospect for a wheat crop, but that prospect 
faded Into nothingness. The Hessian fly got in its work 
to such an extent that the wheat crop was practically 
nothing. The old theory that if wheat Is sown late in 
September the fly cannot hurt it has been completely 
subverted here, as much of it was so sown, and even late 
in October, but the result has been the same. We had 
a remarkably warm, growing Fall, and it seems to have 
suited the fly as well as the wheat. I had a small piece 
sown on October 23, and on November 1 and 2, before that 
wheat had come up, we had about six inches of snow, 
which went off in a day or so. The wheat then came up 
and had quite a season <5f growth. There had not been 
a head of wheat grown In half a mile of that wheat patch 
for 10 years, yet there is fly in it. It would be a matter 
of great interest to readers of The R. N.-Y. if It would 
tell all about the life history of this little pest, and also 
how to get rid of it, if such a thing Is possible. 
White Hall, Ill. 
WHAT THE FLY IS.—One of the worst enemies of 
the wheat plant in nearly every country where wheat 
is grown is a very fragile, dark-colored gnat or midge, 
about an eighth of an inch long, with two wings, 
and resembling quite closely a small mosquito. This 
insect is the famous Hessian fly, so-called, it is said, 
because the evidence points very strongly to the fact 
of its introduction into America in straw brought over 
with the Hessian troops during the War of the 
Revolution. It first appeared in injurious num¬ 
bers in 1779 in the vicinity of the landing place of 
these troops three years before on Long Island, and 
has gradually spread westward following the move¬ 
ment of settlement and wheat culture, reaching the 
Pacific Slope about 1884, and now practically extends 
throughout the wheat belt of the United States and 
Canada. It has long been known on the continent 
of Europe covering the wheat belt from Russia east¬ 
ward. It appeared in England in injurious numbers 
about 1886, and was first thought to have been re¬ 
cently introduced, but has since been proven to have 
been present long before in barley fields. In 1888 it 
was reported from New Zealand, and has since be¬ 
come an important grain pest there, thus nearly 
completing the circuit of the globe. The original 
home of the insect is yet unknown, but there is evi¬ 
dence of its having existed probably from prehistoric 
time in the countries of southern Europe. The Hes¬ 
sian fly is distinctively a wheat insect, but it will 
breed also in barley and rye; and the weight of evi¬ 
dence thus far offered indicates that the insect works 
only in these three plants. The powers of flight 
possessed by the flies are sufficient to provide for 
its ready dispersal over limited areas, and where 
there are continuous or slightly separated plantings 
of wheat, rye, or barley no other means of dispersal 
need be sought. A strong wind could easily help the 
flies over the half-mile stretch, and even farther, sep¬ 
arating the correspondent’s field from the nearest in¬ 
fested plants. The natural spread of the insect in 
this way is said to have been at the rate of about 
20 miles per year in all directions from the center, 
where it started on Long Island. The only other 
means of distribution, and the one by which the insect 
is doubtless transported to distant regions, is by the 
carriage of straw containing the resting stage or 
puparia of the so-called “flaxseeds” of the insect. 
It is believed that the insect landed in America in 
the straw used as bedding by the Hessian troops, and 
that the straw used in tne packing of merchandise 
was the means of its getting to New Zealand. 
HOW IT INCREASES.—Over the bulk of the wheat 
area of the United States there are two principal 
broods of the Hessian fly annually, namely, a Spring 
and a Fall brood. There are, however, supplemental 
broods, both in the Spring and in Fall, particularly 
in the southern wheat areas, but in the extreme 
northern area of the Spring-wheat belt there may be 
only a single annual brood—the progeny of the 
Spring brood passing the late Summer and the Win- 
THE HESSIAN FLY AND ITS WORK. Fig. 198. 
A wheat plant showing an uninjured stalk at left and one in¬ 
fested with Hessian fly at right, the latter dwarfed, leaves with¬ 
ered, and stems swollen at three points near the ground, where 
the “ flaxseeds” are located, between the leaf-sheath and stem. 
a, egg of Hessian fly, 9 greatly enlarged, as are all figures except 
eand/t; ft, the larva-enlarged, the line by the side showing 
natural length; c, the puparium, “ flaxseed,” or pupa case; d, the 
pupa or chrysalis; e, adult female, natural size, ovipositing;/, 
adult female—much enlarged; g, male—much enlarged; h, “ flax¬ 
seed ” in position between leaf-sheath and stalk; i, parasite— 
Merisus destructor, male—enlarged. 
ter in the flaxseed state instead of developing a brood 
in Autumn. It is possible, however, that in this re¬ 
gion an autumnal brood may develop in volunteer 
Spring wheat. In each generation, the insect passes 
through four distinct states or stages, namely, egg, 
maggot or larva, pupa or flaxseed, and mature winged 
insect. These stages are all represented in Fig. 198. 
The eggs are very minute and slender, slightly reddish 
in color and are usually deposited in irregular rows of 
three to five or more on the upper surface of the 
leaf. The number of eggs a single female may lay 
varies from 100 to 150. The whitish maggots hatch 
in a few days, and crawl down the leaf to the base 
of the sheath, there imbed themselves between the 
sheath and stem, and develop on the substance of 
the wheat, causing more or less distortion and bulb¬ 
ous enlargement at the point of attack. In a few 
weeks the larva or maggot contracts into a flaxseed¬ 
like object (see Fig. 198) which i§ the puparium. In 
the case of the Spring brood the Insect remains in 
the flaxseed state during midsummer, yielding the 
perfect insect for the most part in September; in the 
case of the Fall brood the Winter is passed in the base 
of the wheat in the flaxseed condition. The Fall 
brood works in the wheat very near or at the sur¬ 
face of the ground. The Spring brood usually devel¬ 
ops in the lower joints of the wheat, commonly so 
near the ground as to be left in the stubble on har¬ 
vesting. The adults from the wintered-over flax¬ 
seed puparia emerge during April and May, most 
numerously before the middle of the latter month. 
The adults of the important Fall brood emerge chiefly 
during September, but flies may continue to emerge 
until November some years. Most of the individuals 
of the Spring and Fall broods go through the course 
of development just indicated, so that the supple¬ 
mental broods following these are usually compara¬ 
tively unimportant. Under exceptional conditions 
the insect may remain dormant in the flaxseed state 
for a year or more and still bring forth the adult, a 
provision of nature which is doubtless intended to 
prevent the accidental extermination of the species. 
The migrating and scattering brood of adults is the 
one developed in the Fall; the Spring brood does not 
wander much from the field in which it is developed. 
HOW WHEAT IS AFFECTED.—The first indica¬ 
tion in the Fall of the presence of the fly in wheat 
is the much darker color of the leaves and the ten¬ 
dency to stool out rather freely. This is very no¬ 
ticeable, and gives the wheat, for the time being, a 
very healthy appearance. The leaves are broader, 
but the upright central stems are wanting, having 
been killed by the maggot. See Fig. 199. Later the 
infested plants turn yellow or brown, and die in 
part or altogether. The Spring brood of the mag¬ 
gots attacks the tillers or laterals that have escaped 
the Fall broods, dwarfing the stems and weakening 
them so that they usually fall before ripening, and 
cannot be successfully harvested. The development 
of the Hessian fly is much affected by the climatic 
conditions of temperature and moisture, and this 
fact is of much importance in the warfare against 
the insect. Some Autumns are more favorable for 
the development of the insect than others, a mild 
October and November often emphasizing the de¬ 
structiveness of the pest. A damp Spring, even 
though a cold one, is also favorable to the develop¬ 
ment of the insect, while dry, hot Summers are as 
unfavorable, and cause a serious mortality to the 
earlier stages of the Fall brood of adults. It is easy 
to conceive how the correspondent’s field may have 
become inf^ted from a neighbor’s rye, barley, or 
wheat, even though it were half a mile away, as the 
insect could have easily flown that distance with the 
help of the wind. Again, the “remarkably warm 
growing Fall” in A. W. F.’s locality may easily have 
favorably influenced the numbers and destructive¬ 
ness of the insect. 
NATURAL ENEMIES OF THE PEST—The Hes¬ 
sian fly has many natural enemies in the insect world. 
Seven different kinds of insects are known to at- 
