An Unknown Sense 



tion to the most exacting mind. After re- 

 lating them, therefore, I shall return to the 

 subject of special senses, irreducible senses, 

 unknown to us. 



For the moment, let us go back to the 

 Grey Worm, which it would be as well for 

 us to know in a less casual fashion. I have 

 four of them, dug up with the knife at the 

 spots indicated by the Ammophila. My in- 

 tention was to substitute them, by turns, for 

 the doomed victim, so as to see the Wasp's 

 operation repeated. When my plan failed, 

 I placed the worms in a glass jar, with a 

 layer of earth and a lettuce-stalk above them. 

 By day, my captives remained buried in the 

 earth; at night, they came up to the surface, 

 where I caught them gnawing at the salad 

 from below. In August, they dug deep 

 down, not to come up again, and fashioned 

 themselves a cocoon apiece of earth, very 

 rough on the outer surface, oval in shape 

 and the size of a small pigeon's egg. The 

 moth appeared at the end of the same month. 

 I recognized the Dart or Turnip Moth 

 {Nocttia segetum, Hubn.). 



The Hairy Ammophila, therefore, feeds 

 her grubs on the caterpillars of Noctua?; and 

 her choice falls exclusively on the species that 

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