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careful examinations made in 1882, and many times repeated, of the 
earth between the rows, and of the roots of all the weeds growing in 
the field, have failed to discover so much as a single egg outside a space 
a few inches across, around each hill. <A similar careful search of the 
roots of thistles, ragweeds, and goldenrod outside the fields, upon the 
flowers of which the beetles were feeding in great numbers, had a 
similar result; and we have found no evidence in the roots of these 
plants, either in the corn fields or elsewhere, that they have ever been 
infested by the larve. In short, not the shghtest direct proof has thus 
far been found that the beetle breeds anywhere except in fields of corn. 
It is very probable that a few develop in other situations; but the num- 
ber seems to be so small as to defy discovery, except by accident. 
. NATURAL ENEMIES. 
Of natural enemies of this insect, practically nothing is known. 
While in the corn root, the larva is scarcely liable to harm. When 
outside the roots, it has possibly been destroyed now and then by pre- 
daceous insects, which are often numerous in and about hills of corn, 
but dissections of insects of this class (reported in my Twelfth Report), 
do not confirm this supposition. The soft-bodied pupz scattered in the 
earth without special protection of any kind would certainly seem to 
be exposed to insect enemies of this class, but of this fact we have no 
definite evidence. The beetles are not eaten by birds, so far as known 
and our breeding experiments have yielded no insect parasites.* The 
spent adult, female or male, may become infested before death with 
intestinal parasites (Gregarine), and we have occasionally found the 
dead bodies yielding a growth of Sporotrichum globuliferum—a fungus 
paiasite of living insects generally distributed everywhere. 
PREVENTION AND REMEDY. 
A judicious rotation of crops is so simple and complete a preven- 
tive measure, that remedies for injury to corn by the northern corn 
root worm are practically unnecessary. The eggs being laid in corn 
ground in the fall and the larve hatching the following spring, feeding 
so faras known upon nothing else but corn, the planting of such infested 
land to any other grain must inevitably lead to the starvation of tha 
young when they hatch in spring. This is not an inference from the 
life history of the insect merely but even before the time and place of 
oviposition were known, it had been commonly noticed that corn was 
rarely if ever liable to injury by this insect if planted on ground 
which had borne any other kind of crop the preceding year. I have, 
however, some reason to suppose that sorghum and broom corn are not 
good crops to follow with corn when this-root worm is present. 
The frequency of the rotation must depend upon circumstances, 
and especially upon the general abundance of the insect at the time. T 
know of no part of Illinois in which corn is not safe for at least two 
years, and in many situations another year may be added to this period. 
No field on which the crop has already suffered to any noticeable ex- 
"* An assistant, Mr. C. W. Woodworth, reported September, 1885, the finding of 
two small locustids—specimens of which were not brought in—eating the adult Dia- 
brotica. One of these was taken with a half eaten beetle in its jaws. 
~—h 
