252 THE WONDERS OF INSTINCT 



This condition I fulfilled ; and it was rewarded with the 

 success which I was justified in expecting. 



The tubes employed are of two kinds. The first, 

 which are cylindrical and of the same width throughout, 

 will be of use for confirming the facts observed in the 

 first year of my experiments in indoor rearing. The 

 others, the majority, consist of two cylinders which are 

 of very different diameters, set end to end. The front 

 cylinder, the one which projects a little way outside the 

 hive and forms the entrance-hole, varies in width be- 

 tween 8 and 12 millimeters.^ The second, the back one, 

 contained entirely within my packing-case, is closed at 

 its far end and is 5 to 6 millimeters ^ in diameter. Each 

 of the two parts of the double-galleried tunnel, one nar- 

 row and one wide, measures at most a decimeter ^ in 

 length. I thought it advisable to have these short tubes, 

 as the Osmia is thus compelled to select different lodg- 

 ings, each of them being insufficient in itself to accommo- 

 date the total laying. In this way I shall obtain a 

 greater variety in the distribution of the sexes. Lastly, 

 at the mouth of each tube, which projects slightly outside 

 the case, there is a little paper tongue, forming a sort 

 of perch on which the Osmia alights on her arrival and 

 giving easy access to the house. With these facilities, 

 the swarm colonized fifty-two double-galleried tubes, 

 thirty-seven cylindrical tubes, seventy-eight Snail-shells 

 and a few old nests of the Mason-bee of the Shrubs. 



1 Between .312 and .468 inch. — Translator's Note. 

 2.195 to .234 inch. — Translator's Note. 

 3 3.9 inches. — Translator's Note. 



