CH. VI.] THE SOLITARY WASP. HI 



has also completed its tube. The egg is t?ien laid, 

 and the hole carefully filled up and covered with the 

 very sand with which the projecting tube had been 

 made ; the worker is sometimes compelled to leave 

 its work, for the little stock of fluid with which the 

 sand was moistened becomes frequently exhausted, 

 and both Reaumur and Latreille conjecture that it 

 fetches a fresh supply from a neighbouring rivulet, 

 or perhaps sucks a gluing juice from some plant 

 or tree. 



"I have remarked," says the former naturalist, 

 ** that in about an hour a wasp excavated a hole as 

 long as its body, and raised above it a cylinder of 

 equal length : it does not appear that there is a de- 

 terminate depth for every hole, nor are the tubes 

 either of the same length; some are carried on to 

 the length of two inches, and some fall short of one." 



The wasp, no doubt, has a reason for all this : the 

 very fact of the diversity proves a choice ; but what 

 are the reasons which impel it to take the trouble 

 of building a hollow tube out of the material ex 

 cavated ? v/hy not throw away the rubbish 1 



The following are Reaumur's conjectures : — 



" In following this wasp while at work, we can 

 discover at least one of the uses to which the tube 

 is subservient ; the materials of the tube are to the 

 mason-wasp what the heap of mortar is to the 

 brick-layer; the whole depth of the hole is not ne 

 cessary to lodge one egg^ a portion of it being suffi- 

 cient for that purpose. It is proper, however, that 

 the depth should be considerable, lest the rays of 

 the sun should impart too much heat to an egg 

 placed too near the surface. The wasp knows how 

 much of it ought to be left unfilled, the rest is closed 

 with the same sand which had been abstracted in 

 digging it ; and it is in order to have this, as it were, 

 at hand, that the insect takes the pains of forming 

 the tube. 



" But it may be asked, why take the trouble of 



