82 
soria near the middle, usually in line, and about ten very small 
ones irregularly distributed, grouped especially near the apex; 
IV with 5—7 sensoria, one often large, the rest very small; V 
with two or three very small ones and the usual large subapi- 
cal one, and VI with one large and several small ones in a 
group at base of spur, as usual. Tubercles as in the females, 
the thoracic directed outwardly, the cauda as in the females. 
Length 1.4 mm., width .7 mm., antennae .9 mm., cornicles 
.08 mm. 
This species is sufficiently distinguished from Aphis maidis by 
the breadth and large size of the thoracic and abdominal tuber¬ 
cles, which are slender and minute in maidis; by the longer 
beak, which passes the middle coxae and usually attains the 
hind pair, while that of maidis seldom reaches the middle coxae; 
by the cornicles, which have a broad base, the sides tending to 
be straight or concave in outline, while in maidis the base is 
narrower, and the outlines more or less convex, these varying 
somewhat, however, so as to mislead in isolated examples; 
by the cauda, which in the adults is uniformly broadest at base, 
the sides tapering, while in maidis it is somewhat spoon-shaped, 
broad near middle, and narrower between middle and base; by 
the adults of maidis being much more elongate and narrow than 
adults of this species; and, in the winged individuals, by the num¬ 
ber and armament of the sensoria of the third antennal joint, 
which are larger than in maidis and rather uniform in size, six 
to eight in number, and arranged in a fairly straight row, 
while there are thirteen to sixteen visible in maidis , of variable 
size and irregularly distributed along the under side of the joint. 
The oviparous female may be easily recognized by the swollen 
hind tibiae, covered with numerous minute sensoria; and the 
male differs from all the wingless individuals in the presence of 
a few large, and numerous minute, sensoria on the antennae. 
ON THE ANTS ATTENDANT UPON THE CORN ROOT APHIS. 
Lasius niger and its variety alienus are so far the most 
abundant of the seven species of ants which we have found in 
attendance upon the corn root aphis that a discussion of the 
economics of this relation need scarcely take account of any 
other species; but as the most promising protective measures 
against this aphis are based on our knowledge of the life history 
and habits of this commonest corn-field ant, an accurate account 
of the latter is to be desired. Our notes on this subject cover 
the entire period since 1883, and enable me to give a fairly com¬ 
plete history of this species throughout the year. 
Liie History .—The winged sexual forms, male and female, 
of this ant begin to appear each year, as early as the lat¬ 
ter part of June (the 21st to the 27th), hatching from pupae 
which may have formed late in May (27 and 28, by our 
