VARIETIES OF WASP SOCIETY 



possible only in climates where breeding is more or less 

 continuous. In the tropics also, many species of Polistes 

 seem to swarm, though colonies founded by single queens 

 are common too. It seems probable that in Polistes swarms 

 the queen is a young, recently fertilised female and not the 

 old mother as in the honey bee. Much more study of this 

 point is still required. 



This variation in the behaviour of Polistes from north to 

 south may provide an important clue to the origin of social 

 behaviour. A colony in which only one female lays eggs 

 loses a large fraction of the potential birth-rate; the com- 

 pensating advantage is the greater safety and better care of 

 the young. Any auxiliary or worker is an egg-layer lost but 

 a nurse or hunter gained. According to what is the most 

 likely reason for failure of the wasp-colony, it may pay to 

 sacrifice more or fewer queens in favour of nurses. In the 

 north, where climate is perhaps the chief difficulty to be met, 

 direct multiplication may be more important. As climate 

 becomes less severe, it is possible that enemies of various 

 types become more numerous, and it becomes advantageous 

 to sacrifice up to two-thirds of all the queens in order that 

 nests shall be safely founded. 



The process of swarming depends in the first place on a 

 climate sufficiently favourable to allow continuous breeding, 

 or on a worker caste capable of hibernating like the female. 

 On the southern edge of the South American tropics, where 

 the winter is short, whole swarms of Polistes apparently 

 do hibernate together. (The honey bee, of course, with- 

 stands the winter by storing honey for the period when 

 food cannot be obtained.) A few of the Polybia wasps 

 described below are able to do this too, but Polistes never 

 store more than small drops of nectar in some of the cells. 

 Swarming involves a great sacrifice of direct multiplication, 



63 



