224 THE WONDERS OF INSTINCT 



It is as though the authorities had closed the door and 

 affixed to it their great seals of green wax. 



So far then as their building-materials are concerned, 

 the Osmiae whom I have been able to observe are divided 

 into two classes: one building compartments with mud, 

 the other with a green-tinted vegetable putty. To the 

 latter belongs Latreille's Osmia. The first section in- 

 cludes the Horned Osmia and the Three-horned Osmia, 

 both so remarkable for the horny tubercles on their 

 faces. 



The great reed of the south, 'Arundo donax, is often 

 used, in the country, for making rough garden-shelters 

 against the mistral or just for fences. These reeds, the 

 ends of which are chopped off to make them all the 

 same length, are planted perpendicularly in the earth. 

 I have often explored them in the hope of finding 

 Osmia-nests. My search has very seldom succeeded. 

 The failure is easily explained. The partitions and the 

 closing-plug of the Horned and of the Three-horned 

 Osmia are made, as we have seen, of a sort of mud 

 which water instantly reduces to pap. With the upright 

 position of the reeds, the stopper of the opening would 

 receive the rain and would become diluted; the ceilings 

 of the storeys would fall in and the family would perish 

 by drowning. Therefore the Osmia, who knew of these 

 drawbacks before I did, refuses the reeds when they are 

 placed perpendicularly. 



The same reed is used for a second purpose. We 

 make canisses of it, that is to say, hurdles, which, in 

 spring, serve for the rearing of Silkworms and, in 



