Bramble-bees and Others 



the Three-pronged Osmia, who lends herself 

 more readily to laboratory experiment, both 

 because she is stronger and because the same 

 stalk will contain a goodly number of her cells. 

 The first fact to be ascertained is the order of 

 hatching. I take a glass tube, closed at one 

 end, open at the other and of a diameter simi- 

 lar to that of the Osmia's tunnel. In this, I 

 place one above the other, exactly in their 

 natural order, the ten cocoons, or thereabouts, 

 which I extract from a stump of bramble. 

 The operation is performed in winter. The 

 larvae, at that time, have long been enveloped 

 in their silken case. To separate the cocoons 

 from one another, I employ artificial parti- 

 tions consisting of little round disks of sor- 

 ghum, or Indian millet, about half a centimet- 

 re thick.^ This is a white pith, divested of its 

 fibrous wrapper and easy for the Osmia's 

 mandibles to attack. My diaphragms are 

 much thicker than the natural partitions; this 

 is an advantage, as we shall see. In any case, 

 I could not well use thinner ones, for these 

 disks must be able to withstand the pressure 

 of the rammer which places them In position 



^About one-fifth of an inch. — Translator's Note. 



15 



