SHELTERED SITES 



preparation whatever. A nest so fragile that a drop of 

 water would cause it to fall to pieces must of course be built 

 in some place well sheltered from the rain, and we find as 

 a matter of fact that the Osmias almost invariably nest in 

 cavities which afford them ample protection, displaying ex- 

 cellent judgment in their choice. Their nests are often placed 

 in the hollow stems of reeds, usually in those which have been 

 put to some use by man. The reason for this is not difficult 

 to understand. When reeds have been cut down, the part 

 that is left standing offers an ayslum which the insect might 

 enter without any difficulty by way of the divided end, but 

 such a cavity is exposed to falling rain, and that is just what 

 the Osmia ought to avoid. She might, it is true, readily 

 stop up the opening with a plug of mud. She does better 

 than that, however ; she chooses for her abode the part which 

 has been cut off", because she finds it lying flat, and in that 

 position no rain can penetrate into the hollow. On this 

 account Osmias very frequently make their nests inside the 

 straws and reeds of which thatches are composed. 



In their choice of a nesting-place, however, Osmias do not 

 by any means restrict themselves to reeds and rushes, but 

 accept almost any retreat that offers, so long as it meets 

 their requirements as a shelter. Perhaps the most curious 

 of these is an empty snail-shell, the interior of which they 

 divide by means of mud walls into a number of chambers, 

 in each of which an egg is deposited. Failing reeds and 

 snail-shells, they will take possession of the deserted nest 

 of a mason bee, or the galleries which Colletes hollow out of 

 dry banks ; while keyholes and cavities in the woodwork of 

 houses, or glass tubes such as chemists use, do not come 

 amiss to them on occasion, and they will establish them- 

 selves without hesitation in any of these places. Further- 

 more, each species has its own peculiar habits from which it 



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