io6 THE BIOLOGY OF INSECTS 



first filling the neck of the burrow with fine earth which 

 was jammed down with much energy . . . and next 

 arranging the surface of the ground with scrupulous care 

 and sweeping every particle of dust to a distance." Finally, 

 after unsuccessful trials with a small stone and a lump of 

 earth, she laid a leaf over the closed mouth of her burrow. 

 But it is another individual Ammophila that the Peckhams 

 have made famous by observing how, after filling the hole 

 with loose earth and ramming it down with her head, and 

 continuing this process until the hole was full of soil to 

 the ground level : '' she brought a quantity of fine grains of 

 dust to the spot and picking up a small pebble in her 

 mandibles, used it as a hammer in pounding them down 

 with rapid strokes, thus making this spot as hard and firm 

 as the surrounding surface." In connection with this very 

 remarkable incident, it is instructive to note that females of 

 Ammophila sometimes bring small stones to serve as stoppers 

 for the mouths of their burrows. The behaviour of the 

 individuals that have been thus seen to use such stones for 

 pounding down earth may perhaps be regarded as a further 

 advance in the intelligent use of materials serving for nest- 

 making, something beyond the usual habits of their kind. 



Digging wasps paralyse their prey — whether spiders or 

 caterpillars — by stinging the victims repeatedly, frequently 

 applying the sting along the line of the ventral nerve-cord 

 beneath the body. It has often been stated that the opera- 

 tion of stinging is always performed in the same way by all 

 females of the same kind, and that it results in the paralysis 

 of the victim, so that it cannot move, but not in its death, 

 so that the wasp's grubs when hatched will find fresh food 

 in a living though helpless prey. In order to bring about 

 this result it is necessary that the wasp should sting the 

 caterpillar accurately along the ventral nerve-cord so as to 

 pierce the series of ganglia wherein are the nerve-centres 

 that control the movements of the various segments. These 

 considerations have led some enthusiastic naturahsts to 

 imagine that the wasp must have a knowledge of the anatomy 

 of the caterpillar and of the functions of its nervous system. 



