The above evidence is, of course, negative only, and it is not at all — 
certain that the conditions present were ‘such as to favor the migration | 
ot the root lice to the leaves, if this were ever possible. Until further - 
and much more numerous attempts are made to breed the leaf louse 
from the root form, and especially until such attempts are made by 
confining winged root lice of several generations on the leaves and tas- 
sels of corn and sorghum, the relations of these two corn aphides must 
remain somewhat in doubt. 
Disappearance of Corn Leaf Aphis in Fall—To determine the au- 
tumnal history of the leaf louse of corn, two lines of investigation were 
open; the first that of careful and continuous observation of the course 
of events in the field as the season closed and the plant lice disappeared, 
and the second that of insectary and breeding-cage experimentation 
continued through the fall and early winter. Both these lines have been 
carefully worked out under my direction ; the first by Mr. Garman in 
1884, and the second by Mr. J. 8. Terrill, followed by Mr. Marten, in 
the fall and winter of 1888 and 1889. Mr. Garman’s observations ex- 
tended from October 6 to November 20, and were made almost daily 
in corn fields either at Champaign or Normal. As they related to the 
usual lite history of the insect, they will be fully summarized under the 
head of Aphis mardis itself, and it need here only be said that a careful 
following of the stages of the autumnal disappearance of this plant 
louse, as its food dried up and successive frosts destroyed the lingering 
remnants of the summer horde, gave no trace whatever of the presence 
of eggs, or of the occurrence of an oviparous generation. This conclu- 
sion was verified by hundreds of dissections made under the microscope, 
all of which showed the presence of embryos in the abdomen,—and 
also by observations made upon small lots kept alive in the house. The 
experiments of 1888 and 1889, being of an artificial character and re- 
lating to the history of the plant louse under abnormal conditions, may 
properly be given here in full. 
October "9, 1888, adult specimens of Aphis maidis were transferred 
from broom corn to growing Indian corn in pots in the insectary, and 
eight of the lot finally settled upon the corn. Young appeared contin- 
uously, both wingless and winged forms, the latter, however, showing a 
disposition to leave the plant. By October 24 all the plants which had — 
not been covered by bell jars were completely deserted by the lice, and 
under the bell jars the winged lice were evidently disposed to scatter and 
escape, many of them sticking to the glass in the film of moisture which 
covered it within. October 30 these leaf lice were still breeding freely 
on the corn, and likewise on wheat plants exposed to them under the same 
cover, producing both winged and wingless individuals. These condi- 
tions Tagine substantially unchanged, the lice breeding freely in all 
the inclosures in the insectary until March 19, 1889, when the experi- 
ment was discontinued with a considerable supply of these aérial lice 
still in our possession. February 14 one lot under a bell jar was placed 
outdoors to determine the effect of a change of temperature. This lot 
was not examined again until March 4, when all were dead, with no 
trace of eggs, however, on the plants. Between September 11 and 
