2 14 INSECT LIFE xv 



years and years, and then, all at once, I got the 

 opportunity with a facility for observation and clear- 

 ness of detail which made up for the long waiting. 



At the beginning of my observations I succeeded 

 twice in watching the murder of the caterpillar, and 

 saw, as far as the rapidity of the operation allowed, 

 that the sting of the Hymenopteron struck once for 

 all at the fifth or sixth segment of the victim. To 

 confirm this I bethought myself of making sure which 

 ring was stabbed by examining caterpillars which 

 I had not seen sacrificed, but had carried off from 

 their captors while they were being dragged to the 

 burrow ; but it was vain to use a microscope, — no 

 microscope can show any trace of such a wound. This 

 was the plan adopted. The caterpillar being quite 

 still, I tried each segment with the point of a fine 

 needle, measuring the amount of sensibility by the 

 greater or less pain given. Should the needle entirely 

 transpierce the fifth segment or the sixth, there is no 

 movement. But prick even slightly one in front or 

 behind, the caterpillar struggles with a violence pro- 

 portioned to the distance from the poisoned segment. 

 Especially does the least touch on the hinder ones 

 produce frantic contorsions. So there was but one 

 stab, and it was given in the fifth or sixth segment. 



What special reason is there that one or other of 

 these two should be the spot chosen by the assassin ? 

 None in their organisation, but their position is 

 another thing. Omitting the Loopers of Ammophila 

 holosericea, I find that the prey of the others has 

 the following organisation, counting the head as the 

 first segment : — Three pairs of true feet on rings two, 

 three, and four ; four pairs of membranous feet on 



