70 
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 provisionally 
upon the theory of a specific distinction of the root and leaf 
aphides of corn. 
Observations and experiments on the leaf aphis were directed 
especially to the time and circumstances of its earliest appear¬ 
ance in the fields, and to the time and method of its disappear¬ 
ance in fall; to the first with a view to learn whether it origi¬ 
nates 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 trans¬ 
ferring 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. 
Earliest 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 wing¬ 
less adults, pupae, 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 Nor¬ 
mal, Illinois,—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 maidis 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, al¬ 
though 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 produc¬ 
ing 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. Garman 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 thirty growing plants, 
Mr. Marten found a single root aphis dead on the inner surface 
of the leaf. 
Transfer of Root Aphis to the Leaf. —This spontaneous ap¬ 
pearance and breeding of the winged root aphis on the leaves 
of corn was strongly suggestive of a permanent and regular 
