65 
this species moults four times, at average intervals of three or 
four days Our most successful observations upon this and 
several other nice points of individual life history were made on 
isolated specimens, each placed upon the root of a potted plant 
which was then passed through a small glass tube and covered 
with earth except where the tube enclosed it,. To prevent the 
escape of the plant louse the ends of the tube were lightly 
plugged with cotton-wool. 
Migration to Uninfested Fields .—The last autumnal brood of 
the corn root aphis lives, so far as known, only upon roots of 
corn and purslane, the latter being usually infested in com fields 
only, and in these situations, consequently, the eggs are Jett 
from which young hatch the following spring." i his first spt mg 
Generation being always without wings, the root aphis is pi ac¬ 
tually confined for a little time to fields previously in cor n. As 
a considerable part of the second generation acquiies vungs, a 
general dispersal of adults begins almost as soon as the corn is 
out of the ground. These winged root lice do not, however, 
become sufficiently abundant for a considerable time theiea tei 
to noticeably affect fields not in corn the year before. I revious 
to the first of June this distributed attack can scarcely be de¬ 
tected, and not until July 1 have we found it really seiious any¬ 
where. 
The first winded migrant was reared in our breeding rages 
Mav 11, and Mav 12 of another year an example was seen in 
the"field. From this date forward, breeding-cage and held ob¬ 
servations of the winged lice or migrants of this second genei ation 
were an almost daily occurrence to May 28, and were occasional 
for a few days thereafter. 
Many scores of field observations of root lice on corn include 
no case of their occurrence in other than old corn ground pre¬ 
vious to May 19, on which date, in 1887, a single winged louse 
was found on corn after sod. This was on one of the upper 
roots, along which the small brown ant had mined for a- con¬ 
siderable distance. Many other hills in this field were similarly 
mined by ants but contained as yet no plant lice. i\ext, May- 
21 1886, a single winged female was found on corn roots in an 
ants’ nest, the only aphis in the hill, this female began to pro¬ 
duce voung the next day. May 28, among many hills scan heel 
in a "field of corn following upon grass, two were found with 
winged root lice, one of which had just produced a single young 
louse; and May 81 two winged lice were again found m corn 
planted on sod. In the month of June but three such obseiva- 
tions are recorded in our notes, and these refer to small num¬ 
bers onlv. Not until July 1 have we found winged and wingless 
* Amrme- more than fifty lots of “stem mothers” of the corn root aphis col ected by us in 
the field, every one was found in ground which had borne corn for at least ihe year im¬ 
mediately preceding. 
—5 E. 
