XV THE AMMOPHILA 215 



rings seven, eight, nine, and ten, and a last similar 

 pair set on the thirteenth and final ring ; in all eight 

 pairs of feet, the seven first making two marked 

 groups — one of three, the other of four pairs. These 

 two groups are divided by two segments without feet, 

 which are the fifth and sixth. 



Now, to deprive the caterpillar of means of escape, 

 and to render it motionless, will the Hymenopteron 

 dart its sting into each of the eight rings provided 

 with feet ? Especially will it do so when the prey 

 is small and weak ? Certainly not : a single stab will 

 suffice if given in a central spot, whence the torpor 

 produced by the venomous droplet can spread 

 gradually with as little delay as possible into the 

 midst of those segments which bear feet. There can 

 be no doubt which to choose for this single inocula- 

 tion ; it must be the fifth or sixth, which separate 

 the two groups of locomotive rings. The point 

 indicated by rational deduction is also the one 

 adopted by instinct. Finally, let us add that the 

 egg of the Ammophila is invariably laid on the 

 paralysed ring. There, and there alone, can the 

 young larva bite without inducing dangerous con- 

 torsions ; where a needle prick has no effect, the 

 bite of a grub will have none either, and the prey 

 will remain immovable until the nursling has gained 

 strength and can bite farther on without danger. 



With further researches doubts assailed me, not as 

 to my deductions, but as to how widely I might extend 

 them. That many feeble Loopers and other small 

 caterpillars are disabled by a single stab, especially 

 when struck at so favourable a point as the one just 

 named, is very probable in itself, and, moreover, is 



