BEHAVIOR OF SPIDERS AND OTHER INSECTS 421 



conclude : ' The light of this insect cannot, therefore, be taken 

 as phosphorescent. It may be, perhaps, premature to conclude 

 that some rays emitted by these insects are X-iays, but it may 

 be safely asserted that these rays are at least similar to the 

 X-rays and ultra-violet light in so far as they may render cer- 

 tain opaque media transparent and are intercepted by glass." 



Homing. On departing from a place that it is likely to re- 

 visit, Polistes palhpes makes a flight of orientation. This has 

 caused Turner (98) to conclude that associative memory guides 

 this wasp home. 



Respiration. Babak (1) discusses the breathing of Culex. 



Brocher (7, 8, 9) devoted about four years to the study of 

 the respiration of certain aquatic hymenoptera. He paid espe- 

 cial attention to Elmis aeneus. He finds that this species obtains 

 the necessary oxygen, not from the air direct, but from sub- 

 merged plants. Bubbles of air obtained from the plants cling 

 to their bodies. Brocher describes at length the organs by 

 means of which this mode of respiration is carried on. 



MEMORY AND LEARNING BY ASSOCIATION 



Turner (10 1) noticed a digger wasp trying to drag a spider 

 to her nest. In her path she encountered a tall fence, over 

 which, on account of a horizontal scantling, she found it im- 

 possible to drag her burden. Turning about, she dragged the 

 spider along the fence until the corner of the yard was reached. 

 Then she passed through the pickets of the front fence to the 

 outside. Depositing her burden on the ground, she made a 

 flight of orientation and flew off to the nest. Returning, she 

 dragged the spider along the ground towards the nest, and, 

 after overcoming numerous minor hindrances, she succeeded in 

 depositing the spider in her nest. The line by which she finally 

 reached the nest made an angle of about 45 ° with the line along 

 which she originally attempted to drag the spider home. The 

 investigator concludes: 'The behavior of this wasp does not 

 harmonize with the theory that the movements of wasps are 

 tropisms in the sense the term is used by Loeb ; nor is it apparent 

 how it can be the result of what Thorndike calls 'trial and 

 error' movements. Her whole behavior is that of a creature 



