138 
corn is presumptive evidence that the plant has suffered earlier consid- 
erable root injury of the character above described. 
It is very rarely that these phenomena are to be observed-on ground 
not previously in corn, although sorghum and broom corn have been 
found somewhat favorable to the development of this insect. It is 
only where through neglect it has become enormously abundant in a 
field that we may anticipate its escape from the corn in very large 
numbers before it has laid its eggs, in which event, corn not succeeding 
corn may possibly suffer the following year.* The general damage to 
a field is in the worst cases sufficient to destroy the crop so far that the 
disgusted farmer turns his pigs into his corn to get what they can, and 
makes no attempt to harvest his crop. A badly infested field was de- 
seribed to me by Dr. Boardman in 1882, which is worthy of mention 
as illustrating one of the common effects of root injury by this beetle. 
“T should say,” he writes, “that one fourth of the corn in this field was 
rotting or besinning to rot. I found, on cutting an ear open, that I 
could slice the cob as easily as if it were a turnip. The infested corn 
[in Stark county] is yielding from ten to fifteen bushels per acre.’ 
Although the corn root worm beetle is distributed tee the 
Mississippi Valley, and south even to Central America, it clearly be- 
comes comparatively rare southward, and has never been taken by us in 
Southern Illinois in any nufnbers, nor found injurious in the larval 
stage except in the northern two thirds of the State.+ 
This root worm has not heretofore been certainly found infesting 
any other plant than corn,f and the amount of skilled attention which 
has been given to this point by entomologists and other accurate ob- 
servers, makes it practically sure that it is so closely limited to corn at 
the present time in Illinois that we may base our economic methods 
upon the supposition that it infests no other plant. 
FOOD OF THE BEETLE. 
The beetles, beginning to appear in June and continuing until 
November, feed entirely during this whole period upon the-softer and 
more delicate parts of the vegetation present at the time. They collect 
the pollen from the tassels of the corn, or gather that which has sifted 
down among the leaves and collected at their bases, where these join the 
stalk. They also gnaw away the fresh silk from the tip of the ear 
(where they may often be found congregated in numbers of a dozen 
to twenty, or more), probably thus doing a considerable amount of mis- 
* As an example of this tendency to spread from the infested field, I may note 
the not uncommon occurrence at Rankin, Ill., July 1, 1887, of this corn root worm 
in a field of corn following oats, but only on that part of jit which bordered an in- 
fested field in corn the previous year. It is possible that other instances of this 
kind reported previous to 1891 may have related to the southern corn root worm, 
Diabrotica 12-punctata. 
7 I now believe that the statement made by me in 1886 (see ‘‘Entomologica 
Americana,” Vol. II., p. 174) to the effect that I found it injurious to corn in a 
field near Cairo, in Southern Illinois, which had been under water for nearly three 
weeks in the spring, really referred to the southern corn root worm (Diabrotica 12- 
punctata), of whose habit as a corn root insect nothing was at that time known. 
+ A statement from a correspondent, published in my Twelfth Report (p. 19) 
that it is sometimes very abundant in the roots of purslane (Portulaca), I believe 
to have been based on the frequent occurrence in the main root of that plant of the 
burrows of a coleopterous larva resembling the corn root worm, but certainly dif- 
ferent; although never having bred it, I am unable to identify it precisely. It is 
shorter than Diabrotica, and has the mouth parts black instead of brown. 
