364 WASP STUDIES AFIELD 



of grass indicated practical judgment, to say the least. She 

 managed it very ingeniously by lifting one end of the bur- 

 den and propping it high in a fork of grass, then swinging 

 the lower end around to a slightly higher point, and thus 

 continued lifting alternately the ends of the caterpillar until 

 she had hoisted it out of the chasm in the grass thicket, 

 exactly as a man, working alone, would hoist a heavy tim- 

 ber little by little. 



The fact that 5\ pictipennis could not be induced to use 

 the tamping tool until the burrow had been nearly filled 

 shows a marvellous instinct, but the fact that Sphex some- 

 times uses a pebble, a hard clod, a bit of wood or even the 

 leg of a grasshopper, is evidence of highly plastic intel- 

 lectual powers. When she throws in a clod to be ground 

 to dust, she breaks it up; when it is her intention to use 

 it as a tool, she holds it between the mandibles and pounds 

 and rubs it about with a circular motion. Again, when 

 she had left her tool in the depression and had so far for- 

 gotten herself as to kick loose soil over it and bury it, when 

 she was next ready to use it she went back and, with her 

 mandibles, fished out this same clod to use as a hammer on 

 the final layer. 



We have wondered, as have many others, by what sense 

 the wasp locates the proper spot for stinging her prey. 

 We shall not attempt to say how she knows the spot, but 

 the observation of 5\ pictipennis at this critical moment 

 shows that the spot is located by the sense of touch, for 

 she passed the tip of her abdomen on the under-side of the 

 caterpillar, feeling or rather probing in a half-dozen places, 

 sliding her sting continuously backward until she reached 

 the point just to the rear of the last pair of pro-legs and 

 there administered the long, deliberate thrust. 



The flight of orientation as S. pictipennis leaves the nest 

 and the usual return, in contrast to the difficulty and some- 



