SOCIAL LIFE 



83 



Ants also show their ingenuity in caring for herds. 

 This system of stock-raising and dairying can he ob- 

 served by any sharp-eyed student. The herds of the ants, 

 or, as they are sometimes called, the ant cows, are the 

 plant-lice or aphids, such forms as molest your pan- 

 sies. These it is that are cared for by the ants. In 



FIG. 67. "Mud shed" built by ants for sheltering their "herds" of aphids. 

 Photographed from life by M. V. Slingerland. 



some cases they show great forethought in taking the 

 eggs of these aphids into their homes and caring for 

 them, rearing the aphids and carrying them out and 

 placing them in green pastures. The aphids reward the 

 ants for this attention by giving them a s\veet substance 

 generally called honeydew. This substance appears in 

 minute drops upon the back of the aphid. It is fre- 

 quently excreted in quantities sufficient to coat the leaves 



