298 The H^Liiting Wasps 



easily saturated soil. Therefore, in order to con- 

 struct itself an adequate shelter, the larva makes 

 up by its industry for its small quantity of silk. 

 With grains of sand artistically 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, under 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 Scoliae, or sometimes the 

 quantity of silk is insufficient, when they have 

 recourse to gummed sand, this being the method 

 practised by the Bembex, the Stizi and the 

 Palari. A Bembex-cocoon is so compact and 

 strong that it might be taken for the kernel of 

 some seed. The form is cylindrical, with one 

 end rounded and the other pointed. The length 

 is about three-quarters of an inch. On the out- 

 side it is slightly wrinkled and rather coarse to 

 look at ; but the inner walls are glazed with a 

 fine varnish. 



