45 
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Besides this injury to the foliage, another which had had appa¬ 
rently a more disastrous effect upon the growth of the plant was 
evident upon an examination of the roots. In looking over the field, 
patches could be seen here and there in which, nearly every stalk 
was dwarfed, being from six inches to a foot shorter than in other 
parts of the same tract. On pulling up these dwarfed stalks, the 
lowest roots would be found entirely dead, usually only the upper 
circlet of those latest formed giving any sign of life whatever, and 
in some cases only one or two of these would be fresh and soft. In 
fact, fields were visited at this time in which this injury, to what¬ 
ever due, had been so serious that the plants upon acres together 
were either dead or barely alive, hundreds and thousands of 
e stalks which should have been two or three feet high having 
grown not more than five or six inches. In these worst cases, 
usually only one short living rootlet would be found, and this 
always one of the most recent. There was nothing in the ground 
or upon the plant at this time in sufficient abundance to account 
for this condition of the roots, but everything indicated the proba¬ 
bility that it was to be attributed to root forms of the plant-lice 
infesting the leaves and stalks, which had done the mischief at some 
earlier period. If this supposition is correct, it is of course impos¬ 
sible to say how much, if any, of this damage may have been done 
by the single species now under consideration.* 
The preference of this louse for the oldest and lowest leaves of 
the plants attacked by them, is an extraordinary fact, it being the 
common habit of plant-lice to concentrate upon the freshest, tender- 
est and most succulent parts of the vegetation infested by them. 
Although the fields in which this species occurred contained great 
I numbers of a common small yellow ant, (Lasius flavus,) and of a 
still smaller species, (Solenopsis fugax,) it was a remarkable fact that 
neither of these seemed to be paying any special attention to these 
superabundant plant-lice. The Lasius was peculiarly attentive to 
the corn plant-louse at the tips of the stalks, attracted of course 
by the honey-like excretion from the nectaries of this insect; but 
evidently cared nothing for the yellow lice, although these are like¬ 
wise provided with nectaries which must certainly serve for the 
excretion of a similar sweet fluid. 
NATURAL ENEMIES. 
At the time of my visit to Champaign, the natural enemies of 
! these plant-lice were exceedingly few. During several hours search 
[ of the fields, perhaps a dozen eggs of lace-wing flies were seen, 
and a single lace-wing larva. Three or four adult Coccinellidae were 
likewise collected, but not a single larva of this family. Two or 
f three larvae of Syrphus flies were noticed, but, except for these, the 
i plant-lice were left to unrestricted multiplication, within such limits 
as the weather and other general conditions might set. 
‘ t No birds were seen in these sorghum fields except a few chickens 
in the vicinity of one of the houses. Curiously enough, these were 
i actively engaged in devouring the plant-lice, pecking them off the 
*It is not impossible that this injury was of a fungous origin; but characteristic 
examples of it, submitted to Prof. Burrill, did not sustain this view. 
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