VARIETIES OF WASP SOCIETY 



In contrast to the chequered history of this colony is the 

 group of nests of Polybia rejecta which we found hanging 

 from a mango-tree. This tree was covered with enormous 

 ants' nests, probably the separate houses of a single gigantic 

 ant-city. The ants had built a nest of carton, a material 

 composed of earth and wood fibre which is formed into 

 chambers hanging from the branches of the tree. The ants 

 swarmed everywhere, so that it was extremely unpleasant 

 to climb on the tree, though the ants, a species of Dolicho- 

 derus, do not sting, but only bite and squirt poison. On the 

 same tree were at least eight large nests of the Polybia, some 

 of which were certainly one or two years old and probably 

 a good deal older. From the outer branches of the tree were 

 hanging several nests of the Oriole bird or Cassique which 

 frequently joins in this association. It was clear that the 

 Dolichoderus for some reason did not attack the wasps, but 

 they would certainly defend their tree if any horde of driver 

 ants tried to invade it. It is thought that the ants are the first 

 to colonise such trees, and that they provide most of the 

 mutual protection. The wasps come later, and though their 

 stings may make the tree unpleasant to some possible enemies, 

 such as monkeys, they seem to be almost helpless against ants. 



The size of the Polybia colonies is as variable as their 

 appearance. One large group of species make small colonies 

 like those of Polistes, with only a few dozen cells and often 

 only half a dozen wasps. It used to be thought that these 

 colonies were founded by a single queen unaided. But we 

 found that though this was often true, sometimes a very 

 young nest would be occupied by two wasps. Since the cells 

 clearly had never contained a cocoon, neither of the wasps 

 could have been bred in it, and there must have been two 

 founders. We also found that some nests had more than one 

 egg-laying queen, so that the real difference between these 



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