The Mother Decides the Sex 



these impatient ones will leave the home with- 

 out upsetting the shells that are slower in 

 hatching. 



I experimented on Latreille's Osmia, using 

 short and even very short stumps of reed. 

 All that I had to do was to lay them just be- 

 side the nests of the Mason-bee of the Sheds, 

 nests beloved by this particular Osmia. Old, 

 disused hurdles supplied me with reeds in- 

 habited from end to end by the Horned 

 Osmia. In both cases I obtained the same 

 results and the same conclusions as with the 

 Three-horned Osmia. 



I return to the latter, nidifying under my 

 eyes in some old nests of the Mason-bee of 

 the Walls, which I had placed within her 

 reach, mixed up with the tubes. Outside my 

 study, I had never yet seen the Three-horned 

 Osmia adopt that domicile. This may be 

 due to the fact that these nests are isolated 

 one by one in the fields; and the Osmia, who 

 loves to feel herself surrounded by her kin 

 and to work in plenty of company, refuses 

 them because of this isolation. But on my 

 table, finding them close to the tubes in which 

 the others arc working, she adopts them with- 

 out hesitation. 



137 



