: 33 
Spraying.—The discovery of this insect is commonly made only 
when the advancing armies of worms have already entered valuable 
fields of wheat or other grain, and in case of fields so invaded nothing 
of a really practical nature can be done to prevent loss. Such fields 
may be sprinkled, by means of broadcast sprayers, with an arsenical 
solution, or rolled with a heavy roller when the ground is level, or 
pastured by a flock of sheep, which will destroy many of the worms 
by trampling. The arsenical application, however, will probably not 
save the crop, because the worms will eat enough of the crop to 
destroy it before they are themselves killed, and the other measures 
are not applicable in many cases. The main effort under such condi- 
tions should be directed toward preventing the larve from reaching 
other fields. 
Distribution of poison across their line of march.—One of the best 
remedies available in this latter direction is the old-time one of plow- 
ing a furrow with its perpendicular side toward the field ‘to be pro- 
tected and the subsequent dragging of a log 
through the furrow to keep the earth friable 
and kill the worms which have accumulated 
in the ditch; another is to poison heavily with 
Paris green or London purple in solution a 
strip of pasture or field crop in advance of 
the traveling army of worms. In the same 
line is the distribution of quantities of a bran, 
arsenic, and sulphur-sugar mixture across sae eee teers Hea ee 
their line of march. The general destruction _ puparium at right; below is the 
of the worms themselves by direct applica- 7epart of the body of an army 
. : . worm with tachina eggs at 
tions is hardly practicable, and asarule they tachea, somewhat  erilarged 
can be safely left to the action of their natural — (fom Comstock). 
parasites, which at this season are apt to be very much in evidence. 
Natural enemies.—In the case, perhaps, of no other insect of equal 
economic importance is the action of natural enemies more effective 
than with the army worm, and this is especially true when its migra- 
tory instinct drives it forth from its normal protection and concealment 
from its natural enemies in some tuft of rank-growing grass. These 
enemies are species of parasitic tachina flies, rather larger than the 
house fly, which deposit eggs all over the bodies of the larve. From 
these egys maggots hatch and penetrate the larva, feeding on its inter- 
nal organs and eventually destroying it. One of these species, known 
as the red-tailed tachina fly (fig. 20), named after its host, Vemorwa 
leucaniw, may often be seen in hundreds buzzing about a field infested 
with the army worm, and sometimes as many as fifty of its eggs are 
attached to a single caterpillar. So efficient is this fly, as a rule, that 
on occasions of unusual increase of the army worm practically every 
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