XV THE AMMOPHILA 213 



without counting the oesophageal ganglion placed 

 under the skull, and which may be compared to the 

 brain. 



We are here a long way from the nerve centralisa- 

 tion of the Weevil and Buprestis that lends itself 

 so readily to general paralysis by a single stab ; 

 very far too from the thoracic ganglia which the 

 Sphex wounds successively to put a stop to the 

 movements of her crickets. Instead of a single 

 centralised point — instead of three nerve centres — the 

 caterpillar has twelve, separated one from another by 

 the length of a segment and arranged in a ventral 

 chain along the median line of the body. Moreover, 

 as is the rule among lower animals, where the same 

 organ is very often repeated and loses power by 

 diffusion, these various nervous centres are largely 

 independent of each other, each animating its own 

 segment, and are but slightly disturbed by disorder in 

 neighbouring ones. Let one segment lose motion and 

 feeling, yet those uninjured will none the less remain 

 long capable of both. These facts suffice to show 

 the high interest attaching to the murderous pro- 

 ceedings of the Hymenopteron with regard to its prey. 



But if the interest be great, the difficulty of 

 observation is not small. The solitary habits of the 

 Ammophila,— their being scattered singly over wide 

 spaces, and their being almost always met with by 

 mere chance, — almost forbid, as in the case of Sphex 

 occitanica, any experiment being prepared beforehand. 

 Long must a chance be watched for and awaited with 

 unalterable patience, and one must know how in- 

 stantly to profit by it when at last it comes just when 

 least expected. I have waited for such a chance for 



