75 
is, so far as known, 
confined to the 
number. It 
This fungus parasite . 
species of plant lice, of which it infests a great number . It is 
reported by Thaxter, in his “Entomophthorese of the United 
States,”* to occur in Maine, Massachusetts, North Carolina and 
Europe. 
ECONOMIC PROCEDURE. 
Our present knowledge of the life history of the corn plant 
louse suggests four possible methods of attack. (1.) We may 
try the effect of a change of crop after any notable plant- 
louse injury to corn, in the expectation that corn planted on 
oTOund which contains no plant-louse eggs will become so 
slioditlv or so slowly infested, if at all, that no harm need be 
anticipated. (2.) We may resort to fertilizers. and other ap¬ 
plications made to the young corn hili m spring m the hope 
of killing the lice outright or of supporting the plant against 
their attack at a time when this is likely to be most injurious. 
(3 ) Since the small brown ant cares assiduously for the eggs 
in winter and spring, we may assume provisionally the neces¬ 
sity of such care and strive to find means of so disturbing t le 
nests of the ants or of breaking up and dispersing their con¬ 
tents in late fall or in winter that their stores of aplns eggs 
cannot be recovered by them, and so shall be left to pens . 
(4.) Taking account of the early hatching of the eggs in spring, 
—several days, as a rule, before the usual time for planting 
corn,—and the dependence of the young lice for food at that 
time on sprouting weeds in the field,—especially smartweed and 
pigeon-grass,-we may seek to handle the ground in such a 
manner that there shall be no sufficient start of vegetation to 
keep the lice alive. We may also delay somewhat, if neces- 
sary to this end, the planting of the field to corn. 
Rotation of Crops —There can be no doubt that a judicious 
rotation of crops has the effect at least to diminish injury by 
the corn plant louse by distributing its attack; and there is 
also considerable reason to believe that it must result in t e 
destruction, direct or indirect, of a certain proportion of the in¬ 
sects themselves. Corn planted on ground not previously 
stocked with plant-louse eggs must escape at any rate until in¬ 
vaded from without by winged individuals of the second genera¬ 
tion, and then, as a rule, it will be no more subject to injury 
than the other fields in its neighborhood. On the othei 
hand, as the corn root aphis has never been known to infest to 
an injurious extent any other crop following corn there is very 
little probability that the escape of the corn will be balanced by 
damage to other crops. 
We have manv observations going to show that wheat and 
oats and the smaller grass-like plants in general are commonly 
soon deserted by such corn root lice as commence to breed on 
* A full account of this Entomophthora is given in the paper cited. 
Soc. Nat. Hist., Vol. IV., No. 6, p. 168). 
(See Mem. Bost. 
