The Cocoon 



wards the nymph against the Inroads of 

 damp in a shallow and exposed burrow when 

 the rains of autumn come and the snows of 

 winter. Nevertheless, the Bembex' burrow 

 is in a worse plight than that of the Sphex, 

 being situated at a depth of a few inches in 

 easily saturated soil. Therefore, in order 

 to construct itself an adequate shelter, the 

 larva makes up by its industry for its small 

 quantity of silk. With grains of sand art- 

 istically put together and cemented with the 

 silky material it builds itself an exceedingly 

 solid cocoon, impenetrable to damp. 



Three general methods are employed by 

 the Digger-wasps in constructing the sanctum 

 in which the metamorphosis is to take place. 

 Some dig their burrows at great depths, un- 

 der shelter: their cocoon then consists of a 

 single envelope, so thin as to be transparent. 

 This is the case with the Philanthi and the 

 Cerceres. Others are content with a shallow 

 burrow in open ground; but in that case they 

 sometimes have enough silk to increase the 

 number of wrappers for the cocoon, as we 

 see with the Sphex, the Ammophilae and the 

 ScolidB, or sometimes the quantity of silk 

 is insufficient, when they have recourse to 

 gummed sand, this being the method prac- 

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