The Hunting Wasps 



sphere that closes it later are, as we see, but 

 a scaffolding intended to support the ma- 

 sonry of sand and give it a regular curve; 

 they might be compared with the wooden 

 moulds which builders set up when construct- 

 ing an arch, a vault. Once the work is done, 

 the timber frame is taken away and the 

 vault is sustained by virtue of its perfect ba- 

 lance. Even so, when the cocoon is finished, 

 the silken support disappears, partly lost in 

 the masonry, partly destroyed by contact 

 with the coarse earth; and not a trace re- 

 mains of the ingenious method followed in 

 welding together materials with so little con- 

 sistency as sand into a building of such per- 

 fect regularity. 



The round cap closing the mouth of the 

 original eel-trap is a work apart, adjusted to 

 the main body of the cocoon. However 

 well the two parts are fitted and soldered, 

 the solidity is not the same as the larva would 

 obtain if it built its whole dwelling continu- 

 ously. The circumference of the lid there- 

 fore has a circular line of least resistance. 

 But this is not a fault of construction; on the 

 contrary, it is a fresh improvement. The in- 

 sect would find grave difficulty in issuing later 

 from its strong-box, so stout are the walls. 

 328 



