Bramble-bees and Others 



to enter the tube, obviously she will not colon- 

 ize it. She then closes the entrance to this 

 space which she cannot use and does her lay- 

 ing beyond it, in the wide tube. Had I tried 

 to avoid these useless apparatus by choosing 

 tubes of larger calibre, I should have en- 

 countered another drawback: the medium- 

 sized mothers, finding themselves almost com- 

 fortable, would have decided to lodge females 

 there. I had to be prepared for it: as each 

 mother selected her house at will and as I 

 was unable to interfere in her choice, a nar- 

 row tube would be colonized or not according 

 as the Osmia who owned it was or was not 

 able to make her way inside. 



There remain some forty pairs of tubes 

 with both galleries colonized. In these there 

 are two things to take into consideration. 

 The narrow rear tubes of 5 or 55^ milli- 

 metres^ — and these are the most numerous — 

 contain males and males only, but in short 

 series, between one and five. The mother is 

 here so much hampered in her work that they 

 are rarely occupied from end to end; the 

 Osmia seems in a hurry to leave them and to 

 go and colonize the front tube, whose ample 



^.195 to .214 inch. — Translator's Note. 



164 



