6 BULLETIN 8, U. S. DEPARTMENT OF AGRICULTURE. . 
& 
EFFECTS OF ATTACK OF THE LARV. 
The initial effect of the work of the larve in the roots of corn is a 
shortening of the ears, leaving long tips devoid of kernels. As the 
infestation and injury increase, plants fail to develop ears, and 
finally a dwarfing of the stalks occurs. The appearance of the crop 
is precisely the same as it would be if the land were impoverished. 
Indeed many farmers, ignorant of the real trouble, claim that their 
soil has “run out” and is incapable longer of producing corn. One 
farmer insisted that his corn was damaged by careless cultivation. 
For this reason much injury may be done by the pest before it is 
recognized at all. 
NATURAL ENEMIES. 
The Biological Survey has found specimens of Diabrotica longi- 
cornis in stomachs of the nighthawk (Chordeiles virginianus) and 
the wood pewee (J/yiochanes virens). 
The natural enemies of this species are exceedingly few, the prin- 
cipal one being the parasitic fly Celatoria diabroticw Shim., figured in 
Bulletin 5 of this department as an enemy of the adult of the bud- 
worm. Mr. George G. Ainslie, however, has found that the beetles 
are attacked by the so-called chinch-bug fungus, Sporotrichum 
globuliferum. The larvee of the click- beotle Droste elegans Fab. 
are also frequently found among those of this species and may destroy 
some of them. 
CROP ROTATION AS A PREVENTIVE MEASURE. 
In all of the history of this, one of the most destructive pests in 
the cornfield, there is not an instance on record in which corn has 
been injured when planted on land following a crop of small grain, 
such as wheat, rye, barley, or oats. Except on grounds subject to 
overflow, which prevents a rotation of crops so that corn is or must 
be grown for two or more successive years, this pest 1s one of the 
easiest to control. ‘Two instances only need be cited in order to prove 
this fact. 
In Dekalb County evidence of the protection afforded by the rotation of 
crops is afforded on a much larger scale. On a farm of 4,600 acres owned by 
Hon. Lewis Steward, near Plano, rotation of crops has been the regular rule; 
1,600 acres of this land was planted to corn this year, and 700 acres were care- 
fully examined by Mr. Webster. In August only 10 acres of this entire tract 
was found affected by the corn rootworm, and thiS was where, in the rear- 
rangement of the fields, a small tract of ground happened to have been planted 
to corn the previous year. All about Mr. Steward’s place, on farms where 
rotation was not systematically practiced, the damage done was serious and 
general.’ 

1 Quotation from 14th Rept. State Mnt. Ill., p. 29, 1885. 
