240 THE WONDERS OF INSTINCT 



in every respect, to the various species of Mason-bees; 

 and one clear and simple rule stands out from this col- 

 lection of facts. Apart from the strange exception of 

 the Three-pronged Osmia, who mixes the sexes without 

 any order, the Bees whom I studied and probably a crowd 

 of others produce first a continuous series of females and 

 then a continuous series of males, the latter with less 

 provisions and smaller cells. This distribution of the 

 sexes agrees with what we have long known of the Hive- 

 bee, who begins her laying with a long sequence of work- 

 ers, or sterile females, and ends it with a long sequence of 

 males. The analogy continues down to the capacity of 

 the cells and the quantities of provisions. The real fe- 

 males, the Queen-bees, have wax cells incomparably more 

 spacious than the cells of the males and receive a much 

 larger amount of food. Everything therefore demon- 

 strates that we are here in the presence of a general rule. 



Optional Determination of the Sexes 



But does this rule express the whole truth? Is there 

 nothing beyond a laying in two series ? Are the Osmiae, 

 the Chalicodomse and the rest of them fatally bound by 

 this distribution of the sexes into two distinct groups, 

 the male group following upon the female group, with- 

 out any mixing of the two? Is the mother absolutely 

 powerless to make a change in this arrangement, should 

 circumstances require it? 



The Three-pronged Osmia already shows us that the 

 problem is far from being solved. In the same bramble- 

 stump, the two sexes occur very irregularly, as though 



