12 ON THE ORIGIN AND [CHAP. 



the egg, it finds ready a sufficient store of whole- 

 some food. 



Other wasps are social, and, like the bees and ants, 

 dwell together in communities. They live for one 

 season, dying in autumn, except some of the females, 

 which hibernate, awake in the spring, and form new 

 colonies. These, however, do not, under ordinary 

 circumstances, live through a second winter. Cne 

 specimen which I kept tame through last spring and 

 summer, lived until the end of February, but then 

 died. The larvae of wasps (Plate II., Fig. 9) are fat, 

 fleshy, legless grubs. When full-grown they spin for 

 themselves a silken covering, within which they turn 

 into chrysalides. The oval bodies which are so nu- 

 merous in ants' nests, and which are generally called 

 ants' eggs, are really not eggs but cocoons. Ants are 

 very fond of the honey-dew which is formed by the 

 Aphides, and have been seen to tap the Aphides with 

 their antennae, as if to induce them to emit some 

 of the sweet secretion. There is a species of Aphis 

 which lives on the roots of grass, and some ants 

 collect these into their nests, keeping them, in fact, 

 just as we do cows. Moreover they collect the eggs in 

 the autumn and tend them through the winter (when 

 they are of no use) with the same care as their own, 

 so as to have a supply of young Aphides in the spring. 

 This is one of the most remarkable facts I know in the 

 whole history of animal life. One species of red ant 

 does no work for itself, but makes slaves of a black 

 kind, which then do everything for their masters. The 

 slave makers will not even put food into their own 

 mouths, but would starve in the midst of plenty, if they 



