THE SENSES OF INSECTS — McINDOO. 469 



both sexes within the species. Miss Fielde claims that ants not only 

 differentiate the innate odors peculiar to the species, sex, caste, and 

 individual, but also the " incurred " odor of the nest and environ- 

 ment, and furthermore they can detect " progressive " odors due to 

 change of physiological condition with the age of the individual. 

 She says that " as worker ants advance in age their progressive odor 

 intensifies or changes to such a degree that they may be said to 

 attain a new odor every two or three months." 



Wheeler, writing about the odors of ants, says that the specific odor 

 may be readily detected by the blunted human olfactories. Thus the 

 odor of one species is pungent and ethereal; of two other species, 

 smoky; of another species, like the lemon geranium or oil of citro- 

 nella ; of some other species, like mammalian excrement ; and of still 

 other species, like rotten coconuts. 



Concluding from the experiments on ants made by various ob- 

 servers, the family odor in these insects seems to play an important 

 role by enabling the offspring of one queen to distinguish members 

 of their family from those of alien families. Relative to ants, the 

 family odor is probably as important as is the nest odor, but in the 

 honeybee, where certain social habits have been advanced to a higher 

 degree, the family odor is of little or no use, because the hive odor 

 has assumed such an important role in the recognition of the members 

 of the same or of a different colony. Each colony of bees has its 

 own hive odor, a small portion of which adheres to the body of 

 each member of that colony, so that a bee is never entirely devoid of 

 the hive odor. Should workers be forced to remain in the open air 

 for at least three days, which is scarcely possible, they would lose 

 their hive odor, and should they try to enter their own hive they 

 would be attacked by their sister guards, because the family odor 

 emitted by them would not be a sufficient proof to the guards that 

 they were friends; of course if the guards had also lost their hive 

 odor they would let these sisters enter unmolested. 



Now, let us end the discussion concerning the recognition among 

 inserts, based on the olfactory sense, and let us endeavor to locate 

 the olfactory organs. Ever since the time of Aristotle many writers 

 have speculated about the seat of smell in insects, but this subject 

 has been the greatest puzzle of all. The earliest writers, forgetting 

 that the insect organization is entirely different from that in the ver- 

 tebrates, tried to homologize certain parts in insects with correspond- 

 ingly similar parts in the higher animals. Thus the snout, mouth 

 cavity, esophagus, and certain glands in the head were declared by 

 their various advocates to be the proper places for the location of the 

 olfactory organs. When real investigators began to reason and to 

 experiment all of the above imaginary seats were abandoned and the 

 spiracular and antennal views were accepted. Then it was finally 



