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lane, the latter being usually infested in corn fields only, and in these 
situations, consequently, the eggs are left from which young hatch the 
following spring.* ‘This first spring generation being always without 
wings, the root aphis is practically confined for a little time to fields 
previously in corn. As a considerable part of the second generation 
acquires wings, a general dispersal of adults begins almost as soon as the 
corn is out of the ground. ‘These winged root lice do not, however, be- 
come sufficiently abundant for a considerable time thereafter to notice- 
ably affect fields not in corn the year before. Previous to the first of 
June this distributed attack can scarcely be detected, and not until July 
1 have we found it really serious anywhere. 
The first winged migrant was reared in our breeding cages May 11, 
and May 12 of another year an example was seen in the field. From 
this date forward, breeding-cage and field observations of the winged 
lice or migrants of this second generation were an almost daily occur- 
rence to May 28, and were oceasional for a few days thereafter. 
Many scores of field observations of root lice on corn include no 
‘ease of their occurrence in other than old corn ground previous 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 considerable distance. Many other hills in this 
field were similarly mined by ants but contained as yet no plant lice. 
Next, 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 produce 
young the next day. May 28, among many hills searched 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 31 two 
winged lice were again found in corn planted on sod. In the month of 
June but three such observations are recorded in our notes, and these 
refer to'small numbers only. Not until July 1 have we found winged 
and wingless root lice (generations two and three) sufficiently abundant 
in ground not previously in corn to be worthy of special attention. 
The evolution of winged root lice is not confined to the second 
generation, above mentioned, but continues throughout the season in 
numbers varying according to some law not yet ascertained. It is to 
be noted, however, that we have taken the winged form in August but 
once, although our collections of wingless specimens were made on 
twenty-seven days within that month. In September also the winged 
louse is relatively rare, occurring but three times in twenty collections 
made on as many different dates. By November the viviparous genera- 
tions are all dead, as a rule, and the species is thereafter represented only 
by the sexual generation and the egg. 
RELATION TO ANTS. 
Seven kinds of ants have been found by us fulfilling the relation: 
of host, guardian, and nurse to the corn root aphis; viz., Mormica fusca, 
Formica schaufussi, Lasius niger, Lasius niger alienus, Lasius inter- 
jectus, Myrmica scabrinodis, and Solenopsis debilis. The occurrence in 
*Among more than fifty lots of ‘“‘stem mothers’ of the corn root aphis collected 
by us in the field, every one was found in ground which had borne corn for at least 
the year immediately preceding. 
