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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Yol. 13 
“Big Field” at times, depending on the height of the water table and 
upon the temperature of the soil. How much damage is due to the 
presence of water and how much to the billbugs must remain a matter 
of opinion, but the water damage appears to the writer to be essentially 
a halting of the growth of the corn during the higher level of the water 
or during the unfavorably cool weather, especially when the corn is up 
only 3 or 4 inches, as mentioned by Mr. Jenkins, in letter of May 29, 
for 1918 and 1919. Such conditions probably cause some yellowing of 
the foliage without killing the plant or reducing the yield. Incidental 
to the halt in the growth of the plant, the work of any insect will have an 
intensified deleterious effect, provided the conditions retarding growth 
in the plant do not equally retard the insect. As C. pertinax is a swamp 
grass insect, the retarding effect of water on the adult is negligible. 
Referring to Mr. Jenkins’ description of the corn injury, as seen June 
4, we have this statement: “In the infested places all the corn looks 
bad, the leaves cut and wilted, and of a yellow color.” Mr. Painter 
observed the condition of the leaves on June 9, and says the perforated 
appearance of leaves typically injured by billbugs was lost, and the 
leaves of many plants were blown to ribbons, with no apparent expla¬ 
nation. These observations so well represent extreme billbug injury to 
corn foliage as seen at Charleston, Mo., in 1917, where the damage was 
done by C. callosus Oliv. and C. destructor Chttn., both smaller species 
than C. pertinax , that the leaf condition is accepted as adult billbug 
work, 96 per cent C. pertinax. 
Dr. Forbes, in his Eleventh Report, states that the plant injured by 
C. pertinax is less frequently killed outright than by C. aequalis Gyll., 
a larger species, but is commonly dwarfed, often becomes badly twisted 
as it grows, and rarely forms an ear. Mr. Jenkins, in his letter of May 
29, describes this injury when he writes that “some stalks die and 
others finally grow out, later in the summer, but not in time to make 
an ear. ” 
A report from Mr. Jenkins, received December 16, 1919, after he 
had studied the corn damage throughout the season and harvested the 
corn, includes an estimate that the billbug damage was 80 per cent of 
the insect damage and the major part of all the damage. He considers 
that the wetness of the season and of the soil caused the corn to come 
to a stand still, making the work of the insects more disastrous. He 
has already laid considerable tile, which will improve the drainage. 
The plant he referred to earlier as blue flag he now reports is cat-tail, on 
1 plant of which he collected 8 billbugs. Some of the corn made a 
good yield, about 80 bushels per acre, while some was almost a failure. 
The area damaged in 1919 was less than in 1918, when the damage was 
very heavy. 
