THE OSMIiE 233 



until the room is completely furnished. When we have 

 no glass houses at our disposal, we can see these little 

 architectural refinements in the reeds of the hurdles, if 

 we open them at the right season. 



By splitting the bramble-stumps in the course of July, 

 we perceive also that the Three-pronged Osmia, notwith- 

 standing her narrow gallery, follows the same practice 

 as Latreille's Osmia, with a difference. She does not 

 build a party-wall, which the diameter of the cylinder 

 would not permit; she confines herself to putting up a 

 frail circular pad of green putty, as though to limit, be- 

 fore any attempt at harvesting, the space to be occupied 

 by the Bee-bread, whose depth could not be calculated 

 afterwards if the insect did not first mark out its confines. 



If, in order to see the Osmia's nest as a whole, we split 

 a reed lengthwise, taking care not to disturb its contents ; 

 or, better still, if we select for examination the string 

 of cells built in a glass tube, we are forthwith struck by 

 one detail, namely, the uneven distances between the 

 partitions, which are placed almost at right angles to the 

 axis of the cylinder. It is these distances which fix the 

 size of the chambers, which, with a similar base, have 

 different heights and consequently unequal holding- 

 capacities. The bottom partitions, the oldest, are farther 

 apart ; those of the front part, near the orifice, are closer 

 together. Moreover, the provisions are plentiful in the 

 loftier cells, whereas they are niggardly and reduced to 

 one-half or even one-third in the cells of lesser height. 

 Let me say at once that the large cells are destined for the 

 females and the small ones for the males. 



