224 SYSTEMATIC ZOOLOGY 



groups, the true workers and the soldiers, and, like the mature 

 females, they possess a poison gland from which they eject 

 formic acid into the wounds which they inflict. Their nests con- 

 sist of chambers and passages, which they construct in decayed 

 wood or in the earth or in mounds, often of considerable size, 

 which they built. Many ants make definite roads and even 

 construct tunnels below the surface of the ground, often leading 

 from a favorite food supply to their nests. Ants are very fond 

 of the honeydew secreted by the aphids or plant lice, and even 

 keep these insects in their nests as a permanent source of supply. 

 Ants have very highly developed the power of recognizing as 



3 ! 



Fig. 227. Formica rufa, the wood ant. 1, female; 2, male; 3, worker. (After Shipley and 



MacBride.) 



friends the members of their own colony, wherever thev may 

 meet them, and an ant from any other colony is at once recog- 

 nized as an enemy and treated as such. 



The solitary digging wasps deposit their eggs in holes, which 

 they make in the sand or in earth, or in wood, and with the eg 

 they place a sufficient quantity of food to supply the growing- 

 larva. This food consists of other insects or spiders, which the 

 wasp paralyzes by stinging them, often in the large ganglion in 

 the thorax, so that the animal is not killed, but is powerless to 

 move and remains fresh until eaten by the larva. The nests of 

 the social wasps (Fig. 228) are very familiar objects; thev are 

 made of bits of gnawed wood formed into a pulp like paper, and 

 may consist merely of a mass of hexagonal cells or chambers in 

 which the eggs are deposited and the larvae develop. Often, 

 however, these cells are inclosed in a chamber made by succes- 

 sive layers of paper formed about them, with one large openi 

 and these chambers often contain several layers of hexagonal 

 cells ; these cells are generally used for several generations of 

 larva?. As a rule it is only the females that survive the winter, 

 hibernating under stones or logs. 





