COMMUNICATION AMONG INSECTS McINDOO 543 



7. The hive odor (exhalation odor, colony odor). The hive odor is com- 

 posed normally by a mixture of the preceding odors, or of some of them. 

 Single bees, therefore, besides their individual odors, possess the family odor 

 and especially the common, adhering hive odor, which forms the dominant 

 factor in the various actions toward hive mates and strangers — that is, in 

 mutual recognition between bees. 



To support these views, Von Buttel-Reepen gave no proof other 

 than his experiences as a practical beekeeper, which are far from 

 being conclusive when we consider the scientific method; it will be 

 shown, nevertheless, that his views are practically correct so far 

 as they have been tested experimentally. 



After becoming informed concerning the published results on 

 this subject, the present writer in 1913 and 1914 undertook to 

 verify experimentally the views of Von Buttel-Reepen. Such a 

 difficult and complex undertaking he had never attempted before, 

 although it seemed easy before starting, because the way apparently 

 had already been mapped ; all that remained to be done was to go to 

 work. After many preliminary experiments, beset with all kinds 

 of discouraging conditions, the problem proved not so easy as it had 

 been imagined, and instead of becoming simplified it became deeper 

 and more mysterious. What was to be done? Give up in despair? 

 No ; never ! Such is not the way of a scientifically trained investi- 

 gator. Well, then, what? After forgetting all his troubles he 

 went at it again from a different point of view with a determination 

 to win. By this time his own sense of smell had been " sharpened,"' 

 or slightly educated to respond more readily to all the odors around 

 him, so it was decided to start again by smelling the way. 



It was thus determined that the human nose can be trained 

 to recognize a number of characteristic bee odors. At the beginning 

 of his tests the writer was able to distinguish the hive odor, the 

 brood odor (the smell of the larvae and pupae, pi. 1, B, C, D), the 

 honey (A) odor, the pollen or beebread (E) odor, the wax (J) 

 odor, and the odor coming from the bee sting. After a few months' 

 experience he was able to recognize the three castes of bees— queens, 

 drones, and workers — merely by smelling them. 



Old workers constantly give off the characteristic bee odor, and 

 when seized they emit another distinct odor which comes from the 

 poison ejected through the sting. No difference between the odor 

 of a guard (pi. 1, 1) and that of a fanner (G) could be distinguished ; 

 the odor from each closely resembles the hive odor ; that is, the odor 

 which comes out of a hive when the hive cover is removed. A worker 

 carrying pollen gives off besides the bee odor another odor which 

 comes from the pollen. 



The younger the workers are the less pronounced is the bee odor 

 emitted. To the human nose the odor emitted by nurse bees (pi. 1, 



