71 
migration, and of a possible transformation there into > the ordU 
nary Aphis maidis in late June or early July. This hypothesis 
was"tested by a series of experiments made in 1890.and T • 
the most conclusive of which was begun June 22 of the lattei 
velr Corn growing in a trench in the insectary was stocked 
with root lice from the field, several “adult females being confined 
to the leaf in a bag of Swiss muslin* From this beginning, the 
successive generations were bred, specimens of each generation 
being transferred to a new leaf, until September ib (at which 
time the sexual generation appeared) without the &hght • <.1 
proximation in any generation to the characters of the aenal 
Anhis maidis. Several similar experiments made with sorghum 
plants instead of corn were even less successful, transferred root 
lice though living and breeding for a short time, dll ln _, 
nevertheless, in from ten to sixteen days without more definite 
result. From these experiments we may conclude with some con¬ 
fidence that the corn leaf aphis does not originate in a nugia- 
tion of wingless lice from the roots.! 
Another class of experiments, less precise but Jess artificial 
noint to a similar conclusion concerning the winged loot louse 
also In these experiments large rectangular frames coveied 
with cheese cloth were used to enclose tightly entire hi s of 
corn in the field, as well as specially planted hills m a plot o 
o-round adjoining my insectarv. In the field experiments these 
screens were made without doors the hills bemg p en i u j 
stocked with corn root lice in the beginning, and with then t- 
tendant ants, before the screens were set. In J h J* ft nsed when 
corn was left to itself until a sufficient time had elapsed, when 
the cover was removed and the plant searched for the corn leaf 
louse. In the small garden plot a screen was built large enoug 
to enclose four hills of corn at once. At first the mistake w as 
made of using too small a frame, and our results m 1' 1 * 
vitiated by the discovery that winged ApAis maidw Jom the 
fields would sometimes settle on the cheese cloth co 
the corn leaves pressed against it, and there extrude their youn^, 
which were small enough to pass through the mes ies i Fie 
cloth Thereafter the enclosure was made so large that no pa 
of the plant could touch it, even when full grown access to t 
plants being given by means of a closely fitting door. The : 
experiments of this series were the following Six coin hills 
were covered in the field June 28, 1889, selected because already 
stocked with the corn root aphis and the small brown ant 
Lasias ni<*er alienns attending it. July 15 one hill was opened 
up and found unchanged, except that the ants; had b ^J'°" e e 
under ground and come to the surface far outside the space en 
closed, thus providing for themselves and their chaiges <i na< \ 
* On account of a deficiency in the notes of this experiment, it is now impossible to say 
whether any winged females were included in this lot. , . 
t Our notes of breeding case work and ob^Uoneinthe fjeldshow. nevertheless 
and in another upon the leaves, at a much greater 
distance, where young were being produced. 
