The Mother Decides the Sex 



a sex that is entitled to but the smallest con- 

 sideration. Besides, the two sexes must be 

 represented in almost equal numbers. The 

 Osmia decides upon one female, whose por- 

 tion shall be the better room, the lower one, 

 which is larger, better-protected and more 

 nicely polished, and one male, whose portion 

 shall be the upper storey, a cramped attic, 

 uneven and rugged In the part which en- 

 croaches on the bottle-neck. This decision is 

 proved by numerous undeniable facts. Both 

 Osmi[E therefore can choose the sex of the 

 egg about to be laid, seeing that they are now 

 breaking up the laying Into groups of two, a 

 female and a male, as required by the condi- 

 tions of the lodging. 



I have only once found I.atreillc's Osmia 

 established in the nest of the Masked Antho- 

 phora. She had occupied only a small num- 

 ber of cells, because the others were not 

 free, being inhabited by the Anthophora. The 

 cells in question were divided Into three 

 storeys by partitions of green mortar; the 

 lower storey was occupied by a female, the 

 two others by males, with smaller cocoons. 



I came to an even more remarkable ex- 

 ample. Two Anthidia of my district, An- 



149 



