SOLITARY AND SOCIAL WASPS 



by a single female and the individuals are either males or fully 

 fertile females. In the social species, at least some of the 

 females are relatively or quite infertile and these assist in the 

 care of the young of the fully fertile females, or queens. The 

 females with reduced fertility are almost always quite incap- 

 able of fertilisation by the males and form the worker caste. 

 A further feature in which the solitary wasps differ from the 

 social ones is that the female rarely lives much longer 

 than the male, and successive generations of adults hardly 

 overlap. 



The most familiar social wasps in Britain and North 

 America are species of the genus Vespula. These will be 

 described first, although some of the less familiar tropical 

 species have simpler behaviour and seem to come nearer to 

 the solitary species. These common wasps have two sorts 

 of females, the egg-laying queens and the workers. The latter 

 are considerably smaller than the queens, have a slightly 

 different pattern tff yellow markings, and are not fertilised. 

 Males occur for a rather short period at the end of the sum- 

 mer, when they fertilise the young queens of the next genera- 

 tion. The workers cannot correctly be described as sterile, 

 since some of them may lay eggs, especially towards the end 

 of the season or even sooner if the queen dies ; but these 

 unfertilised eggs produce only males, so that the workers 

 alone could not carry on the species. 



The young fertilised queens may stay for a little time in the 

 nest where they were born, but quite soon they begin search- 

 ing for winter quarters, since they are the only members of 

 the colony which hibernate. At the first frosts or earlier, the 

 males and workers die off and all that is left is the young 

 queens hiding in the ground, under dead leaves, or under 

 bark. A few of them may try to hide indoors, but it is usually 

 too dry for them there and the warmth prevents them from 



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