HYMENOPTERA. 
64I 
nests beneath large flat stones. It is a curious fact that in 
a single nest some of the pupae will be enclosed in cocoons 
while others are naked. This ant is not always accompanied 
by slaves; but it is a common occurrence to find its dark- 
colored associate with it. The way in which this ant gets its 
slaves has been described above (p. 638). 
The Slave-ant, Formica subsericea (F. sub-se-ric'e-a).— 
This is usually a dark-brown or ash-colored ant with reddish 
legs, but it varies greatly in color. It generally makes its 
nest in the ground, beneath a stone or other object, and 
leads an independent life when allowed to do so. But it is 
this species that Formica difficilis enslaves. 
The Corn-louse Ant, Lasins brunneus (Las'i-us brun'ne- 
us).—This is the common, brown, small ant, about one eighth 
inch in length, whose nests abound along the borders of 
roads, in pastures, and in meadows. It is an exceedingly 
interesting species on account of the care it is known to 
take of certain plant-lice that feed upon the roots of grass 
and of grain. One of these plant-lice feeds on the roots of 
corn, and is a very serious pest in the middle West. It has 
been discovered that this ant cares for the eggs of this plant- 
louse, keeping them in its nest during the winter, thus 
making sure of having a herd of Aphids from which it can 
get a supply of honey-dew the following summer. 
The marriage flights of the ants of the genus Lasius are 
remarkable. The nests of these ants are so inconspicuous 
that they are rarely observed except when search is made 
for them. But the males and young queens from all the 
nests in one region will emerge at one time, usually some 
warm afternoon, and, where a short time before no ants 
could be seen, the air becomes filled with these flying crea¬ 
tures. We have ridden for several miles through such a 
swarm, when the ants were so abundant that it was almost 
impossible to breathe without inhaling them. The ants that 
make up these swarms are very different from the workers 
that we find in the nests. Both the young queens and the 
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