328 PROCEEDINGS OF THE ACADEMY OF [Apr., 



winged forms of Formica. The quicker reaction time of Formica is 

 probably due to the fact that Formica is more agile than Camponotus. 

 Based on reaction times, the small workers of Campofiotus smell 

 slightly better than their large sisters. Judging from the total 

 number of pores, the winged forms of any species of ants smell 

 considerably better than the workers of the same species. 



Among the wasps the relative sensitiveness is tolerably well 

 graduated from the lowest to the highest species as listed in the 

 table. Instead of the two social wasps, Polistes and Vespula, having 

 the highest relative sensitiveness, they seem to take second place, 

 while the first place is held by the guest wasp, Pseudomasaris, and 

 the solitary wasp, Monohia. 



Among the bees the relative sensitiveness is also tolerably well 

 graduated from Andrena, the lowest examined, to Apis, the highest. 

 This system of calculating shows that the worker honey bee smells 

 considerably better than the queen and equally as well as the drone. 

 Reaction times show that drones smell slightly better than workers 

 and considerably better than queens. It is thus seen that the honey 

 bee has. the most highly developed olfactory sense of the Hymenop- 

 tera, while that of ants is considerably inferior. 



Based upon reaction times, the relative sensitiveness to odors of 

 insects depends not only upon their ability to receive odor stimuli, 

 but also upon their agility and sluggishness in responding when the 

 olfactory organs are stimulated. To illustrate this point, the 

 workers of Camponotus are more agile than the workers of Apis, and 

 for this reason probably alone they respond more quickly to odors. 

 Judging from only their reaction times, the former smell better than 

 the latter, but in all probability the reverse is the truth. The ability 

 to receive odor stimuli depends upon the development of the entire 

 nervous system, including the olfactory apparatus, and upon the 

 physiological state of the insect being tested. At the mating time 

 the winged females of ants certainly smell as well and probably much 

 better than the workers of the same species. As long as the recently 

 fertilized females perform all duties necessary in bringing their first 

 brood to maturity, they certainly retain almost the same degree of 

 acuteness in smelling as before; but when they become a mere egg- 

 laying machine and perform none of the nest duties, their ability to 

 receive odor stimuli is probably less acute. It is thus seen that the 

 physiological state is an important factor when the relative sensi- 

 tiveness is considered, and we have little means of knowing just 

 what physiological condition a given insect is in when it is being 



