HYMENOPTERA. 641 



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, Lasius 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 w4s 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 



