Basis of Sex Determination 223 



in which the workers are sterile and smaller than the 

 real females. In such a society of wasps all the males 

 and workers die in the fall and only the fertilized 

 females survive, each one founding a new nest in the 

 following spring. From the first eggs laid, workers 

 arise, small in stature and sterile; these workers are 

 nourished by their mother. Then these workers take 

 care of the feeding of all those larvas which arise from 

 the eggs which their mother continues to lay. Through- 

 out the spring only workers arise from the eggs. The 

 males appear in the summer, the real females towards 

 the end of the season when the sexes copulate. 



Marchal isolated a number of the sterile workers, 

 providing them with food but giving them no larvas 

 to raise. He found that the workers which thus far 

 had been sterile became fertile, producing, however, 

 only males. This latter fact is easily understood from 

 what has been said regarding the bees, namely, that 

 the female produces only one type of eggs, hence the 

 unfertilized egg can give rise only to males. The 

 astonishing or important point is that the ovaries of 

 the workers begin to develop as soon as they no longer 

 have a chance to nourish the larvas, provided the food 

 which would have been given to the larvas is now at 

 their disposal. In other words, the development of 

 their ovaries is the outcome of eating the food which 

 under normal conditions they would have given to the 

 larvas. The food must, therefore, contain a substance 



