TOWER OF THE SAND- WASP. 171 



depth. Every two or three minutes, however, during these 

 operations, it takes a short excursion, for the purpose probably 

 of replenishing its store of fluid wherewith to moisten the sand. 

 Yet so little time is lost, that Reaumur has seen a mason-wasp 

 dig in an hour a hole the length of its body, and at the same 

 time build as much of its round tower. 



" For the greater part of its height this round tower is per- 

 pendicular, but towards the summit it bends into a curve, 

 corresponding to the bend of the insect's body, which, in all 

 cases of insect architecture, is the model followed. The pellets 

 which form the walls of the tower are not very nicely joined, 

 and numerous vacuities are left between them, giving it the 

 appearance of filigree-work. 



" That it should be thus slightly built is not surprising, for 

 it is intended as a temporary structure for protecting the insect 

 while it is excavating its hole, and as a pile of materials, well 

 arranged and ready at hand, for the completion of the interior 

 building, — in the same way that workmen make a regular pile 

 of bricks near the spot where they are going to build. This 

 seems, in fact, to be the main design of the tower, which is 

 taken down as expeditiously as it has been reared. 



" Reaumur thinks, that by piling in the sand which has pre- 

 viously been dug out, the wasp intends to guard its progeny 

 for a time from being exposed to the too violent heat of the 

 sun; and he has sometimes even seen that there were not 

 sufficient materials in the tower, in which case the wasp had 

 recourse to the rubbish she had thrown out after the tower was 

 completed. By raising a tower of the materials which she 

 excavates, the wasp produces the same shelter from external 

 heat as a human being would who chose to inhabit a deep 

 cellar of a high house. 



" She further protects her progeny from the ichneumon-fly, 

 as the engineer constructs an outwork to render more difficult 

 the approach of an enemy to the citadel. Reaumur has seen 

 this indefatigable enemy of the wasp peep into the mouth of 

 the tower, and then retreat, apparently frightened at the depth 

 of the cell which she was anxious to invade." 



It is no wonder that the Sand- wasp should be so anxious to 

 insure the safety of her nest, for her foes are multitudinous. 

 Putting aside the ordinary Ichneumon-flies, we have the pre- 



