NO. 2 RECOGNITION AMONG INSECTS — McINDOO 33 



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 (1913, p. 182) writing about the odors of ants says : 



The specific odor may be readily detected even by the blunted human olfac- 

 tories. Thus the odor of Formica rtifa is pungent and ethereal, of Hypoclinea 

 gagates and mariee smoky, of Acanthomyops like the lemon geranium or oil 

 of citronella, of the species of Eciton and some Pheidole, like mammalian 

 excrement, of Cremastogaster lineolata fainter but equally unpleasant, of 

 Tapinoma like rotten cocoa-nuts, etc. Undoubtedly ants are very quick to 

 react to these various odors as well as to the " nest-aura," or odor which 

 every colony derives from its immediate environment, brood, etc. 



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 

 honey-bee 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 and 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. 



Howlett (1915), endeavoring to lure the fruit fly, Bactrocera 

 (Dacus), by using various chemicals, gives the following three prob- 

 able explanations why the male flies are attracted so remarkably to 

 methyl-eugenol and iso-eugenol : ( i ) The odors emitted from these 

 substances may closely resemble the odors emitted by the females, 

 and therefore they would serve as a sexual guide; (2) these odors 

 may also resemble those emitted by certain plants, and in this case 

 they would attract the females to the proper plants for breeding pur- 

 poses ; and (3) in a second case the odors would attract both sexes 

 to these plants in order that the insects obtain suitable food. 



