THE OSMLE 235 



primogeniture. And so it goes on, story by story, until 

 the cylinder is full. Then the thick plug of the same 

 green material of which the partitions are formed closes 

 the home and keeps out marauders. 



In this common cradle, the chronological order of 

 births is perfectly clear. The first-born of the family is 

 at the bottom of the series; the last-born is at the top, 

 near the closed door. The others follow from bottom 

 to top in the same order in which they followed in point 

 of time. The laying is numbered automatically; each 

 cocoon tells us its respective age by the place which it 

 occupies. 



A number of eggs bordering on fifteen represents the 

 entire family of an Osmia, and my observations enable 

 me to state that the distribution of the sexes is not gov- 

 erned by any rule. All that I can say in general is that 

 the complete series begins with females and nearly al- 

 ways ends with males. The incomplete series those 

 which the insect has laid in various places can teach 

 us nothing in this respect, for they are only fragments 

 starting we know not whence ; and it is impossible to tell 

 whether they should be ascribed to the beginning, to the 

 end, or to an intermediate period of the laying. To sum 

 up : in the laying of the Three-pronged Osmia, no order 

 governs the succession of the sexes; only, the series has 

 a marked tendency to begin with females and to finish 

 with males. 



The mother occupies herself at the start with the 

 stronger sex, the more necessary, the better-gifted, the 

 female sex, to which she devotes the first flush of her 



