The Life of the Caterpillar 



There you have the centre-bit of your boring- 

 tool. 



To make our tunnels in granitic rocks we 

 tip our drills with diamond points. For a 

 similar task the Bombyx, a living drill, wears 

 implanted on her forehead a row of crescents, 

 hard and durable as steel, a regular twist- 

 bit. Without suspecting its use, Reaumur 

 was perfectly aware of this marvellous im- 

 plement, which he called scaly stairs : 



"What does it profit this Moth," he asks, 

 "that she should thus have the front of her 

 head formed like scaly stairs? That is just 

 what I do not know." 



My test-tubes, learned master, will tell us. 

 By good fortune, of the numerous Moths as- 

 cending from the bottom of my apparatus 

 through a column of sand solidified by the 

 evaporation of the original moisture, some are 

 making their way upwards against the side 

 of the tube, enabling me to follow their ma- 

 noeuvres. I see them raising their cylindrical 

 bodies, butting with their heads, jerking now 

 in one direction, now in another. The nature 

 of their task is obvious. The centre-bits, with 

 an alternating movement, are boring into the 

 agglutinated sand. The powdery wreckage 



