INSTINCTS IN WASPS 147 



He took some of the crickets and introduced poison into 

 their bodies with a needle. When this was done indiscrimi- 

 nately, that is, in no particular part of the animal's body, 

 it either killed the animal or produced very temporary 

 results, according to the amount of poison introduced. 

 When, however, he introduced the needle into the three 

 nervous centres (thoracic ganglia) which control the move- 

 ments of the insect, he found that complete paralysis 

 ensued. More than this the metabolism was checked, and 

 the paralysed insect continued to live without food for 

 several weeks, which it certainly could not have done under 

 normal conditions. An interesting point about this instinct 

 of Sphex is that the prey is stung at one particular point 

 where the tissues are soft and the nerve centres are easily 

 reached from the surface. Much the same thing happens 

 in the case of Ammophila, and its prey the caterpillars, 

 only here the wasp has to apply its sting many times, so 

 that all the middle segments at least of the animal's body 

 are paralysed. 



Now the supporters of the theory that acquired characters 

 are transmitted say that it is impossible to account for the 

 origin of these instincts in any other way than that the 

 ancestors of the existing wasps first exercised a certain 

 amount of intelligence. A wasp found that when it stung 

 a grasshopper in a particular place, that grasshopper was 

 paralysed and was much more easily carried to the nest. 

 It remembered this, and led by past experience, always 

 stung its prey in the same place. This habit produced ah 

 effect on the germplasm, and the offspring tended to sting 

 their prey in the same manner until the instinct became 

 established, and so no longer depended upon the intelligent 

 action of the wasp. This interpretation, however, appears 

 to break down when carefully considered. To begin with, 

 it assumes that intelligent action preceded instincts. We 

 find that the higher we go in the animal kingdom, the 

 fewer the instincts and the greater the intelligence. We 

 only find intelligent action as a very late product in evolu- 



