50 
Seven species of plant lice belonging to as many different genera,* 
have been found by us habitually infesting corn roots in Illinois. They 
are Aphis maidiradicis, Schizoneura panicola, Trama erigeronensis, 
Forda occidentalis, Tychea brevicornis, Rhizobius spicatus, and Geoica 
sguamosa. By far the most important of these is the first mentioned, 
commonly known as the corn root aphis. This is, in fact, the only one. 
on the list which infests corn primarily as a principal food plant, the 
others being essentially species of the meadow and pasture, attacking 
corn but lightly, and most commonly only when it follows grass. — 
The association of all these species with ants, which care for them 
in many ways, some of them indispensable, and feed in turn on excre- 
tions of their insect charges, is a fact of special economic significance, 
since the ant most active in preserving the plant louse species must be 
taken into account as a factor in the economic problem. 
Tue Corn Root APHIS. 
(Aphis maidiradicis, Forbes.) 
(Plate VII., Fig. 5 and 6; and Plate VIII., Fig. 1-5.)7 
No insect affecting corn is more deserving of the attention of farm- 
ers and entomologists at the present time than the corn root aphis. It 
ranks as a corn pest with the chinch bug and the army worm, less in- 
jurious at any one time than these are locally and occasionally, but over- 
taking them, on the other hand, by its general distribution and the con- 
stancy of its attack. Although it lives upon the roots throughout the 
life of the plant, the principal damage is done at the same time as that 
caused by wireworms—while the corn is still small. It contrasts with 
the corn root worms with respect to the time of its most injurious ac- 
tivity, the latter coming in at about the time when the aphis generally 
begins to loosen its hold; but the two agree in the fact that they make 
their first appearance in spring only on ground which has been in corn 
for at least a year preceding. The common root worm is confined 
throughout the season to the field in which it hatches, while the aphis 
presently scatters abroad, more or less freely according to the percent- 
age of the second and succeeding generations which develop wings. On 
* The following brief table may serve in a general way to indicate the correct 
genus and species of each of our corn root lice: ; fr: 
@ornicles: well@developeds. = fa. ce wate ooalegs ate acehslatetere milsseuwiey aivtens Aphis maidiradicis. 
Cornicles reduced to dark rihgs...:........+.sé..u- ....-Schizoneura panicola. 
Cornicles wanting. 
Last two joints of beak not longer than basal portion, 
Anal plate subglobose, strongly prominent. 
Third antennal joint about as long as first two combined, an addi- 
tional joint usually more or less distinctly formed from it, making 
the antenne 6-jointed............j0...-.6. =. Trama erigeronensis. 
Third antennal joint very long, nearly twice as long as first two com- 
bined, antenne uniformly 5-jointed........... Forda occidentalis. 
Anal plate short, transverse, not at all prominent. 
Antenne normal, as large as rostrum, third and fifth joints more 
than twice longer than thick...=-.......:...- Tychea brevicornis. 
Antennz minute, much smaller than rostrum, joints less than twice 
AS VONEs BSN CK iv melee Cohn © sate, ye. Syopseyenses toteiely Rhizobius spicatus. 
Last two joints of beak much longer than basal portion, anal plate retracted 
+ A colored plate of the oviparous females, and of winged, wingless, and pupa 
forms of the viviparous female of this species, was published in the 17th Report of 
this office. : 
