73 
abundant on stalks and leaves of the plant in the cage with the 
ants, and this condition of things continued until September 16, 
when the experiment was dropped. Apart from the negative re¬ 
sult of this attempt to bring the corn leaf aphis out of the root 
louse, we get additional evidence that the latter does not thrive 
on the sorghum root. 
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 of 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 tassels of corn and sor¬ 
ghum, the relations of these two corn aphides must remain 
somewhat in doubt. 
Disappearance of Corn Leaf Aphis in Fall .—To determine the 
autumnal history of the leaf louse of corn, two lines of investi¬ 
gation were open; the first that of careful and continuous ob¬ 
servation 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. barman in 
1884, and the second by Mr. J. S. Terrill, followed by Mr. Mar¬ 
ten, in the fall and winter of 1888 and 1889. Mr. barman s 
observations extended 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 life history of the insect, 
they will be fully summarized under the head of Aphis maidis 
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 genera¬ 
tion. This conclusion 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 relating 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 trans¬ 
ferred from broom corn to growing Indian corn in pots in the 
insectary, and eight of the lot finally settled upon the corn. 
Young appeared continuously, 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 
