XV THE AMMOPHILA 207 



arc choice material — blocks ready prepared to stop 

 up the dwelling by and by. 



This outside work is done with a self-contained 

 air and great diligence. High on its legs, its 

 abdomen outstretched at the end of its long petiole, it 

 turns round and moves its whole body at once with 

 the geometrical stiffness of a line revolving on itself. 

 If it has to throw away to a distance the rubbish 

 it decides to be only encumbrances, it does this with 

 little silent flights, often backwards, as if, having 

 come out of the shaft tail first, it thought to save 

 time by not turning round. Species with long- 

 stalked bodies, like A. sabulosa and A. argentata, 

 are those that chiefly display this automaton-like 

 rigidity. Their abdomen, enlarged to a pear-shape 

 at the end of a thread, is very troublesome to manage ; 

 a sudden movement might injure the fine stalk, 

 and the insect has to walk with a kind of geometrical 

 precision, and if it flies, it goes backward to avoid 

 tacking too often. On the other hand, A. hirsuta, 

 which has an abdomen with a short petiole, works 

 at its burrow with swift easy movements such as 

 one admires in most of the miners. It can move 

 more freely, not being embarrassed by its abdomen. 



The dwelling is hollowed out. Later on, when 

 the sun has passed from the spot where the hole is 

 bored, the Ammophila is sure to visit the little heap 

 of stones set aside during her burrowing, intent to 

 choose some bit which suits her. If she can find 

 nothing that will do she explores round about, and 

 soon discovers what she wants — namely, a small flat 

 stone rather larger than the mouth of her well. 

 She carries it off in her mandibles, and for the time 



