53 
them, and so far as my observations have extended, can scarcely be 
called injurious to them. It has been observed in the field, however, or 
bred in the insectary, on the roots of a number of other species of plants, 
some of which are, in fact, important to its maintenance. Many of the 
first generation hatch from the egg in the field before the corn is ready 
to receive them, and at this time young smartweed plants and foxtail 
grass (Polygonum and Setaria) are their principal resource. ‘These 
plants harden early and lose the succulence ie ; makes them especially 
desirable to plant lice, a fact which cee laren 1 part no doubt for the 
early transfer of the lice to corn; but i ( Aelae of small grain, Setaria 
and Polygonum may continue to sgn the corn root louse at least 
until the second generation is well matured. Indeed, I have found this 
insect on the roots of smartweed more than a foot high as late as June 
1%. Crab-grass (Panicum) also becomes infested, but less abundantly 
than the Setaria, and from the latter part of June throughout the rest 
of the season the aphis breeds abundantly on the common purslane 
(Portulaca oleracea). We have occasionally found it so abundant on 
purslane plants far removed from corn fields—besides paths in lawns 
and in other similar situations—that one might well regard this as a 
purslane aphis, if it were not for the fact that this weed starts too late 
in the season to serve as food for the ear hee generations. 
We have, further, experimental evidence that the corn root aphis 
can live on roots of ragweed (Ambrosia), having transferred May 8, 
1889, half-grown young of the second generation from smartweed roots 
to this plant, where they lived and fed until they acquired wings, five 
days later. The fall oviparous generation and the one preceding it have 
been repeatedly reported by my field assistants—who were constantly 
dealing with the root aphis and knew its characters perfectly—to have 
abundantly infested dock (Rumea crispus), fleabane (Hrigeron cana- 
dense), mustard (Brassica nigra), sorrel (Oxalis stricta), plantain 
(Plantago major), Hungarian grass (Setaria germanica), pigweed 
(Amarantus hybridus), and squash ; but as these statements were not 
verified by successful transfers from these various plants to corn, they 
rest only on determinative evidence, notoriously unreliable with respect 
to the plant louse species. Indeed, an attempt at transfers of the sup- 
posed corn aphis found on squash, sent me from Ohio by Prof. C. M. 
Weed, entirely failed. A similar result was reached in an attempt to 
transfer known corn root lice from corn to wheat and oats, begun April 
22, 1889. Insects placed on roots of wheat in breeding cages April 22 
continued to live there until May 5, but without producing young. May 
11, however, all had left the plants. An earlier experiment, beeun April 
10, had a like ending, and a precisely similar result was obtained in a 
parallel experiment with oats. 
The repugnance of this insect to the roots of small grain was re- 
peatedly shown also by field observations. Fields of oats and wheat on 
old corn ground, sometimes known to have been badly infested by the 
root aphis the preceding year, often contained in April and May large 
numbers of these root lice and their associated ants, the former feeding 
on the roots of smartweed and pigeon-grass growing with the grain, but 
