eye NS ete 
“68 
‘stantially fulfilled for the root louse only, as will be seen from what is 
presently to follow. The leaf louse, on the other hand, although it has 
been carried through the greater part of the year, including the entire 
fall and winter season, has never yet been seen to produce a sexual gen- 
eration or an egg. Some experimental evidence has been obtained by at- 
tempting to bring the leaf aphis out of the root form by breeding the 
latter for many successive generations upon the corn leaf, and by similar 
attempts to rear the root louse from, the winged leaf louse transferred 
to the roots of corn. These attempts have not thus far succeeded, and as 
the case stands at present, there is no satisfactory evidence of the specific 
identity of these forms, but a considerable body of proof to the contrary. 
The economic recommendations of this paper are therefore based pro- 
visionally upon the theory of a specific distinction of the root and leaf 
aphides of corn. 
Observations and experiments on the leaf aphis were directed es- 
pecially to the time and circumstances of its earliest appearance in the 
fields, and to the time and method of its disappearance in fall; to the 
first with a view to learn whether it originates in migrants from the 
roots; and to the second in the hope of finding the sexual generation, 
and thus determining the place of deposit of its eggs. A few additional 
experiments in transferring the leaf aphis to the roots of corn and other 
plants were made to see whether we could thus demonstrate the possi- 
bility of a migration downward from leaf to root and the origin of the 
root louse from that of the leaf. 
Harliest Appearance of the Corn Leaf Aphis——The earliest date 
at which the leaf louse has been found by us is July 23 (1883), at which 
time it was common in a field of sorghum near Champaign. It occurred 
there in all stages of winged and wingless adults, pupa, and young, in 
association with the yellow sorghum louse (Chaitophorus flavus). It had 
doubtless started there as early as July 15. 
Our next earliest date for the leaf aphis is July 28 (1884), when 
wingless females were found by Mr. H. Garman at Normal, Ilinois,— 
the first specimens of the year,—beneath the lower leaves of small corn 
in the field. Many stalks were searched, but the aphis was found in 
only two. Again, July 31, 1888, winged examples of Aphis maidts 
were common, crawling about on stalks and leaves of corn in a field near 
Urbana, Illinois. 
Protracted and most careful search in corn fields which were heavily 
infested by the root aphis, made by Mr. C. M. Weed during the latter 
days of June, 1887, and by Mr. John Marten early in July, 1889, failed 
to discover a single leaf louse, although Mr. Weed found the winged root 
louse on corn leaves June 23, 24, 27, 29, and 30. In several cases these 
winged lice had made themselves at home upon the leaf, and were pro- 
ducing young, from one to five occurring with a single female. June 
30 several winged root lice were detected on the rolled corn leaves at 
the tip of the stalk. Indeed, numerous earlier observations of winged 
root lice on leaves of corn are recorded in our notes; one by Mr. Gar- 
man as early as June 6, and others June 9 and June 11. On the last 
date, after tearing open the terminal tufts and rolled leaves of some 
