THE FACTORS WHICH DETERMINE SEX 665 



organs never fully develop, but royal diet stimulates these organs 

 to grow so that the larvae become queens. A partially developed 

 worker may be made partially fertile by supplying it with some of 

 the jelly obtained from a royal cell. The following table shows the 

 relative composition of the solid food given to workers and queens^: — • 



Solid Food. 



Nitrogenous 



Fatty 



Glucose 



This table shows that the quantity of fatty material supplied to the 

 developing queens is very nearly double that given to the workers. 



.There is no evidence that drone larvte can be converted into 

 females by a supply of royal or other food, so that the case of bees 

 can scarcely be regarded as affording a real instance of sex being 

 determined by, conditions of nutrition, since workers are true females 

 whose reproductive organs and other sexual characteristics have 

 failed to develop owing to an insufficiency of stimulating food. 



The case of white ants or termites is probably comparable, though 

 considerably more complicated, since the different kinds of sexual 

 individuals are more numerous. The young may develop into 

 workers, soldiers, or royal substitutes, and the latter may be further 

 transformed into fully fertile or "royal" individuals, while both 

 sexes (i.e. males and females) are represented in each of these forms. 

 Grassi's observations ^ point strongly to the conclusion that these 

 different kinds of individuals are developed from similar eggs under 

 different conditions of nutrition which is supplied to the young by 

 the older members of the community; but here again there is no 

 evidence that males can be converted into females or females into 

 males. 



Eolph ^ has describisd a series of observations on the production 

 of males and females in Nematus ventricosus, a species of sawfly. 

 These observations sho\V that the percentage of females in broods of 

 larvae reared from fertilised ova steadily increased from June to 

 August and then proceeded to diminish. " We may conclude without 

 scruple, that the production of females from fertilised ova increases 

 with the temperature and with the food supply (Assimilationsleistung), 



' Geddes and Thomson, loc, cit. 



2 Grassi and Sandias, "The Condition and Development of the Society of 

 Termites," Quar. Jour. Mwr. Science, vols, zxxix. and xl., 1896-97. 

 ^ Eolph, Biologisohe Prohleme, Leipzig, 1884. 



