MUTUAL AID AND COMMUNAL LIFE 425 



of the little brown ant. The following spring before the 

 corn is planted, these eggs hatch. Now, the httle brown 

 ant is especially fond of the honey dew secreted by the com 

 root lice. So when the latter hatch in the spring, before 

 there are corn roots for them to feed on, the ants carefully 

 place them on the roots of certain kinds of grass and knot- 

 weed {Setaria, Polygonum) and there protect them until 

 the corn germinates. They are then removed to the roots 

 of the corn. It is probable that the ants even collect the 

 eggs of the aphids in the autumn and carry them into their 

 nests for protection and care. 



The studies of Wheeler and others have revealed some 

 interesting cases of the living together of different species 

 of ants. In some cases one of the ant species may be living 

 almost wholly at the expense of the other species, as does 

 the little yellow thief-ant, Solenopsis molesta. Although 

 this ant sometimes lives in independent nests, more often it 

 is to be found living in association with some large ant 

 species — it consorts with many different hosts — feeding 

 almost exclusively on the live larvae and pupae of the host. 

 The thief-ant is so small and obscurely colored that it seems 

 to live in the nests of its host practically unperceived. The 

 Solenopsis nest may be found by the side of- the host nest, 

 around it, or partly in it, the tiny Solenopsis galleries ramify- 

 ing through the nest mass of the host, and often opening 

 boldly into these large galleries. Through their narrower 

 passages, too narrow to be traversed by the hosts, the tiny 

 thief-ants thread their way through the host nest in their 

 burglarious excursions. 



But there are numerous cases of a less one-sided advantage 

 in the association of different species. As an example, the 

 conditions exhibited by the red-brown ant, Myrmica brevi- 

 nodes and the smaller Leptothorax emersoni (conditions made 

 known by Wheeler's careful observations) may be briefly 

 described. The little Leptothorax ants live in the Myrmica 



