THE OSMLE 261 



that the Osmia, penetrating as far down as the helical 

 passage permits, finds, immediately above the point which 

 is too narrow to pass, the space necessary for the cell 

 of a female. This cell is succeeded by others, wider 

 still, always for females, arranged in a line in the same 

 way as in a straight tube. In the last whorl of the 

 spiral, the diameter would be too great for a single row. 

 Then longitudinal partitions are added to the transverse 

 partitions, the whole resulting in cells of unequal dimen- 

 sions in which males predominate, mixed with a few 

 females in the lower stories. The sequence of the sexes 

 is therefore what it would be in a straight tube and espe- 

 cially in a tube with a wide bore, where the partitioning 

 is complicated by subdivisions on the same level. A 

 single Snail-shell contains room for six or eight cells. 

 A large, rough earthen stopper finishes the nest at the 

 entrance to the shell. 



As a dwelling of this sort could show us nothing new, 

 I chose for my swarm the Garden Snail (Helix ccespi- 

 fow), whose shell, shaped like a small swollen Ammonite, 

 widens by slow degrees, the diameter of the usable por- 

 tion, right up to the mouth, being hardly greater than 

 that required by a male Osmia-cocoon. Moreover, the 

 widest part, in which a female might find room, has to 

 receive a thick stopping-plug, below which there will 

 often be a free space. Under all these conditions, the 

 house will hardly suit any but males arranged one after 

 the other. 



The collection of shells placed at the foot of each hive 

 includes specimens of different sizes. The smallest are 



