TRACHEA TA 



383 



males, females,' and workers ; the last-named are females which 

 sometimes produce parthenogenetic eggs. These colonies are 



Fig. 216. — Nest of Vespa sylvestris. 



annual, existing for the summer only. In the autumn all die, 



with the exception of a few fertilised females, which creep into 



crevices of trees or under stones, 



and hibernate through the winter. 



In the spring the female emerges 



and commences to build a nest; 



this is constructed of fragments of 



wood gnawed up and mixed with 



saliva, the whole making a papery 



substance. As soon as two or 



three cells are finished the female 



lays an egg in each, and when the 



white apodal grubs hatch out they have to be fed, whilst at 



the same time the mother is widening and deepening their 



cells and adding others. 



The larval stage lasts about two weeks, and then the grubs 



Fig. 217.— Fespa rufa. 



