Bramble-bees and Others 



more clearly than ever, her power of deciding 

 the sex of the egg, in order to adapt it ju- 

 diciously to the conditions of the house-room 

 available. 



I had offered at the same time to the 

 Osmiae in my study some old nests of the 

 Mason-bee of the Shrubs, which are clay 

 spheroids with cylindrical cavities in them. 

 These cavities are formed, as in the old nests 

 of the Mason-bee of the Pebbles, of the cell 

 properly so-called and of the exit-way which 

 the perfect insect cut through the outer coat- 

 ing at the time of its deliverance. Their diam- 

 eter is about 7 millimetres;^ their depth at 

 the centre of the heap is 23 millimetres" and 

 at the edge averages 14 millimetres.^ 



The deep central cells receive only the fe- 

 males of the Osmia; sometimes even the two 

 sexes together, with a partition in the middle, 

 the female occupying the lower and the male 

 the upper storey. True, in such cases eco- 

 nomy of space is strained to the utmost, the 

 apartments provided by the Mason-bee of the 

 Shrubs being very small already, despite their 



^.273 inch.— Translnior's Note. 

 '.897 inch. — Translator's Note. 

 •^.546 inch. — Translator's Note. 



140 



