Bramble-bees and Others 



one Is represented by a column of sand 50 

 millimetres^ deep and the top one by a column 

 of 15 millimetres." The holding-capacity of 

 the one is therefore about three times as large 

 as that of the other. The cocoons enclosed 

 present the same disparity. The bottom one 

 is big, the top one small. Lastly, the lower 

 one belongs to a female Osmia and the up- 

 per to a male Osmia. 



Occasionally the length of the bottle-neck 

 allows of a fresh arrangement and the cavity 

 is divided into three storeys. The bottom 

 one, which is always the most spacious, con- 

 tains a female; the two above, both smaller 

 than the first and one smaller than the other, 

 contain males. 



Let us keep to the first case, which is al- 

 ways the most frequent. The Osmia is in 

 the presence of one of these pear-shaped hol- 

 lows. It is a find that must be employed to 

 the best advantage: a prize of this sort is 

 rare and falls only to fortune's favourites. 

 To lodge two females in it at once is impos- 

 sible; there Is not sufficient room. To lodge 

 two males In it would be undue generosity to 



^1.95 inches. — Translator's Note. 

 2.585 inch. — Translator's Note. 



148 



