SOLITARY AND SOCIAL WASPS 



stragglers being found in the nest up to some date in October. 

 According to Duncan, nests sometimes survive much longer 

 in the mild winters of California, and may even survive the 

 winter. 



Besides the sort of cannibalism described above, there 

 appears also to be some eating of eggs, probably both by the 

 queen and by workers. Such behaviour is common in most 

 of the social insects, and a queen will sometimes eat her own 

 eggs soon after laying them. As will be explained in chapter 

 7, egg-eating may sometimes tend to protect the colony 

 against parasites which try to lay their own eggs in the cells ; 

 some egg-eating may be the price which has to be paid for a 

 type of instinctive behaviour which is at other times socially 

 valuable. It is also certain that the regulation of the number 

 of eggs is essential to the well-being of the colony, and egg- 

 eating might be regarded as a form of birth-control. It is 

 unlikely, however, that either of these explanations can cover 

 all the facts. In most insects some of the B vitamins are 

 essential for growth and normal health, and it is possible 

 that the eggs are a source of such substances. The needs of 

 wasps for vitamins have not yet been studied. 



Later in the season the workers, or some of them, may lay 

 a number of unfertilised eggs, and unlike the queen they may 

 lay more than one in the same cell. If the queen dies, worker 

 laying may occur on a much larger scale and will lead to the 

 production of many male wasps. 



It is a familiar fact that some years are " wasp years " 

 whereas in other years wasps are scarce. This seems to be 

 due much more to the number of nests which are successfully 

 established in the spring than to the number of queens pro- 

 duced in the autumn. In other words, the hazards of hiber- 

 nation are less than those encountered during colony- 

 foundation in the spring. For this reason, the campaigns 



55 



