16 PROTECTION OF PLANTS, 1915-16 



to tropisms. Tropic reactions are obligatory and predictable, but Infusor- 

 ians not only respond to stimuli but they put into practice the method of 

 trial and error, which to a large extent dominates their behaviour. 



Is this behaviour the emergence of intelligent behaviour among animals? 

 If so, then among multicellular animals lower than vertebrates account 

 must be taken of intelligence which has a modifying influence on instinctive 

 actions. Instances of this interaction are numerous among insects. Bees 

 sometimes cut a hole through the base of long-tubed flowers as an easy way 

 of securing the nectar. Many of the actions of ants and wasps can be ex- 

 plained on the theory that they show some degree of intelligence. They 

 profit by experience and are able to choose bet^^een alternatives. 



The late J. H. Fabre, the great French student of insect life, who gave 

 a long life to the close observation of the ways of insects, looks upon the 

 instinct as different from reflex action and intelligence, and as something 

 implanted in insects at the outset, and not derived from anything else. In his 

 "Souvenirs Entomologiques" he gives numerous examples of the actions 

 of insects. The action of the Sphex wasp in provisioning her home with 

 paralysed crickets, if instinctive, shows considerable intelligence. That the 

 intelligence is limited is shown by Fabre's experiment in removing the cricket 

 a short distance from the entrance while the wasp was inspecting the burrow as 

 was its custom. The wasp on its return found the cricket, brought it again 

 to the entrance, but went again on an inspection of the burrow. Fabre 

 removed the cricket forty times and the wasp went through the same 

 routine. 



The Digger Wasp, Ammophila, provides its young with live cater- 

 pillars which she first paralyses. This action, like that of the Sphex wasp, 

 is not automatic but one of routine, and if this routine be disturbed every- 

 thing goes wrong. 



Fabre cites other cases of disturbed routine. He covered a wasp's 

 nest with a bell-jar. The inmates were unable to get out because it was 

 not part of their routine to dig under the jar. He joined the front and hind 

 ends of a file of procession caterpillars, and "they went circling round and 

 round the stone curb of a big vase in the garden day after day for a week." 



Fabre also placed a slight paper cap over the lid of a mason bee's cell. 

 So long as the cap was in contact with the lid the maggot had no difficulty 

 in making its way out, but if a small space is left between the cap and the 

 lid the maggot failed to escape. 



