THE SOCIAL INSECTS 



become very familiar with the surroundings of the nest since 

 many, sometimes all, her cells are in the same spot. 



A third group, the Eumenids, resemble the social wasps in 

 many details of structure, but build nests very like those of 

 the sand wasps. They have one habit which has been 

 retained in the social species : the egg is laid in an empty 

 cell and the prey, which are paralysed caterpillars or beetle 

 grubs, are brought in afterwards. 



These methods of providing for the young are known as 

 mass-provisioning, since the egg is enclosed in a cell with 

 enough food for it to complete its development. The food 

 is supplied whole, in the form of paralysed or sometimes dead 

 insects. A few species both of sand wasps and of the Eumenid 

 wasps show an important advance in behaviour; they 

 practise progressive provisioning. These wasps lay an egg 

 either on the first prey brought in or in the empty cell and 

 then wait until the egg hatches before bringing more food. 

 In this way the mother has some contact with her young. 

 Ammophila pubescens, already described, provides one of 

 the best known examples of such behaviour. In some of the 

 other species which practise progressive provisioning, such 

 as the African wasp Synagris, the female may feed her 

 young with chewed fragments of prey instead of whole 

 specimens. 



SOCIAL WASPS 



It is from wasps with this sort of equipment, though not 

 from any living solitary species, that we imagine that the 

 social species arose. The ancestors of the social wasps were 

 thus sting-bearing hunters, capable of building nests of some 

 complexity, capable of learning their location with great 

 exactness, and beginning to have some contact with their 

 young. However, in the solitary species each nest is made 



44 



