362 ENTOMOLOGY 



instinct in favor of such more precise terms as pkototropism, 

 geotropism, etc. ; though the term instinct remains useful as 

 applied to an action that is the resultant of several tropic 

 responses. 



The modern student of instincts aims to resolve them into 

 their component reflexes and to determine as precisely as pos- 

 sible the influence of each reflex component. Thanks to the 

 labors of a great number of skilled investigators, we are no 

 longer satisfied to class an action as " instinctive " and then 

 dismiss it from thought; for now we are in a position to 

 'analyze the action, and may hope to explain it eventually in 

 terms of the physical and chemical properties of protoplasm. 



3. INTELLIGENCE 



Though manifestly dominant, pure instinct fails to account 

 for all insect behavior. The ability of an insect to profit by 

 experience indicates some degree of intelligence. 



Take, for example, the precision with which bees or wasps 

 find their way back to the nest. This is no longer to be 

 accounted for on the assumption of a mysterious " sense of 

 direction," for there is the best of evidence for believing that 

 it depends upon the recognition of surrounding objects. 

 When leaving the nest for the first time, these insects make 

 " locality studies," which are often elaborate. Referring to 

 Sphex ichneumonea, the Peckhams write : " At last, the nest 

 dug, she was ready to go out and seek for her store of pro- 

 vision and now came a most thorough and systematic study 

 of the surroundings. The nests that had been made and then 

 deserted had been left without any circling. Evidently she 

 was conscious of the difference and meant, now, to take all 

 necessary precautions against losing her way. She flew in and 

 out among the plants first in narrow circles near the surface 

 of the ground, and now in wider and wider ones as she rose 

 higher in the air, until at last she took a straight line and 

 disappeared in the distance. The diagram [Fig. 291, A] 

 gives a tracing of her first study preparatory to departure. 



