30 INSECT ARCHITECTURE. 



The sort of sand-bank which it selects is hard and 

 compact ; and though this may be more difficult to 

 penetrate, the walls are not liable to fall down upon 

 the litlle miner. In such a bank, the mason-wasp 

 bores a tubular gallery two or three inches deep. 

 The sand upon which Reaumur found some of these 

 wasps at work was almost as hard as stone, and 

 yielded with difficulty to his nail ; but the wasps dug 

 into it with ease, having- recourse, as he ascertained, 

 to the ingenious device of moistening it by letting 

 fall two or three drops of fluid from their mouth, 

 which rendered the mass ductile, and the separation 

 of the grains easy to the double pickaxe of the little 

 pioneers. 



When this wasp has detached a few grains of the 

 moistened sand, it kneads them together into a 

 pellet about the size of one of the seeds of a goose- 

 berry. With the first pfcllet which it detaches, it 

 lays the foundation of a round tower, as an out- 

 work, immediately over the mouth of its nest. 

 Every pellet which it afterwards carries off from 

 the interior is added to the wall of this outer round 

 tower, which advances in height as the hole in the 

 sand increases in 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 wherewitii 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 perpendicular; but towards the sum- 

 mit 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 be- 



