72 
means of escape from confinement, as well as a passageway for 
the possible introduction of other plant lice from without. 
July 25 and 30 two other hills were opened a/nd found un¬ 
changed. From a fourth hill, examined August 2, and a fifth, 
opened September 2, everything had escaped, neither ants nor 
plant lice remaining; while the sixth, opened September 11 
contained an abundance of the root aphis (winged adults and 
young) as well as the usual ants. In all these cases a critical 
examination of the entire plant above ground showed bevond 
question the absence of the aerial aphis. 
In the large breeding cage near the insectary, corn was planted 
early in May, 1890, and the hills were stocked June 3 and 4 
with ants, ant larvae, and root lice, others being added to the 
original stock June 13, July 1, 10, and 16, August 2 and 18, 
and September 15. These repeated additions were made neces¬ 
sary by the gradual disappearance of the root lice from the 
plants, which did not thrive perfectly at first, owing apparently 
to the shade of the screen. No aerial lice appeared in this cage 
at any time during the progress of the experiment. This was 
terminated October 5, at which time root lice were still present 
on the corn. 
In another experiment, made June 16, 1891, by transferring 
the same species to hills of planted corn in the enclosure above 
described, the same results appeared. Root lice were reared on 
all the hills throughout the entire summer, but there was no 
appearance of aerial lice at any time up to September 16, when 
the experiment closed. 
In 1891 both corn and sorghum were grown in this enclosure 
for experiment, and the plants were first stocked June 16. Ad¬ 
ditional specimens of both the root aphis and the small brown 
ant were introduced June 27 and 29 and July 17, and ants 
alone, including their pupae, larvae, and eggs, July 24. By ex¬ 
posing single roots in little cavities in the earth and covering 
these with glass, it was easy to watch the behavior of the in¬ 
sects after they had been put in place, and it was thus learned 
that the sorghum hills were deserted almost at once. Conse¬ 
quently no root lice were found on the sorghum roots when the 
plants were dug up July 13 and September 16. On the corn, 
however, the root aphis continued until the experiment was 
closed at the date last mentioned, but no aerial lice appeared at 
any time on either kind of plant. 
Another smaller experiment was tried with a hill of sorghum 
only, transplanted to a box July 3, stocked with the root aphis 
and with ants of all stages, and covered with Swiss muslin. July 
10 and August 1 more root lice were added, and July 17 both 
lice and ants. Ants were observed at work in this enclosure July 
11, 18, 20, 22, and 30, August 5, 7, 10, 15, and 18, and Sep¬ 
tember 1 and 16; but no aerial corn lice appeared at any time, 
and no corn root lice were seen after August 5. August 18 the 
common yellow sorghum louse (Cliaitophorus flavus) had become 
