OBSERVATIONS ON INSECT LIFE 193 



must be fulfilled. The caterpillar cannot be removed 

 until sting and jaw have done their work. The 

 paralyzed larva must be again paralyzed, the crushed 

 head must be again crushed before the next step in 

 the instinctive round can follow and the caterpillar 

 can be dragged into the cell. 



The closure of the nest supplies a second instance 

 of the utter folly of the insect when, through any 

 interference, the instinctive round is broken. A 

 caterpillar has been carried to the nest, dragged 

 below, an egg has been laid and the wasp is now 

 industriously engaged in sealing up the tunnel. First 

 it spreads a roof over the buried chamber to provide 

 a safe nest for the growing egg. For this it selects 

 what is suitable from the soil around. A bulky pebble 

 or a few flat laminae of slate serve the purpose and 

 are pushed down into the pit. The wasp follows, 

 moulds them into place by the pressure of her head 

 until the cell is closed. The roof secure, any material 

 serves to block the tunnel. Surrounding debris, dust 

 or sand or pebble, is shuffled indiscriminately down the 

 passage. More is poured in ; everything is swept 

 backward into the pit. All it needs is to be pressed 

 tight ; the tunnel wall must be a consolidated, not a 

 crumbling structure. Down goes the insect's head, 

 the legs clutch the sides of the tunnel, the wings 

 vibrate, and, with the vertex as a ram and all the 

 strength of the body as a driving force, the loose 

 particles of crumbling earth are compressed into a 

 solid mass. Again the debris is poured in, again the 

 process of consolidation follows. The stoppage of 

 the tunnel is half complete and the wasp rests. It 

 flies off to a neighbouring bank of flowers. It will 



