16 DONALDSON BO DINE. 



tologists have failed to denionstrnte any organs near the spiracles of 

 insects which could be supposed to act as organs of smell, also lends 

 argument against the idea of a current of air caused by respiration. 

 Indeed, if the current is of any advantage, may it not be possible 

 that the waving of the antenna so familiar to all observers would 

 provide for it in sufficient degree. 



Many experiments have been made upon insects to determine 

 whether the antennae are really scent organs. In most cases Cole- 

 optera or Hymenoptera have been used because of their greater ease 

 of manipulation. The most valuable experiments are those con- 

 ducted by Hauser and described by him in the " Zeitschrift fur wis- 

 senschaftliche Zoologie," Bd. 34. Auguste Forel* and Sir John 

 Lubbockf have also performed many interesting and instructive 

 experiments. These investigators believe that the sense of smell 

 does reside in the antennae. Some of them also believe that there 

 may be other parts of the body or other organs which are sensitive 

 to impressions of smell. Some experimenters have arrived at a con- 

 trary conclusion. Many of them, however, have in their tests made 

 use of strong odors, often of irritating and corrosive substances, and, 

 in consideration of the extreme delicacy of the sense being tested, it 

 seems to me that their results are untrustworthy. 



I have dwelt at such lengtli upon the question of smell because 

 its possession is of such great moment to the Lepidoptera not only 

 in the detection of the whereabouts of their food, but in the more 

 important problem of the perpetuation of their species. A review 

 of all the arguments pro and con has forced the conviction upon me 

 that the pits and rods, and probably the cones also, are the special 

 organs of this sense. No other organs so well adapted are found in 

 the insect and the number occurring in an antenna seems to be cor- 

 related with the importance of the use of scent in the life of the 

 species. Hauser;}; says the bees and wasps have 14,000 to 15,000 

 cavities and about 200 cones in each antenna ; the leaf wasps, a 

 smaller number. The flesh and dirt flies have 60 to 150, while the 

 flies that live on plants have only 5 or 6 to each feeler. 



Hearing. — It is frequently denied that Lepidoptera possess the 

 sense of hearing, and evidently they pay little attention to the ordi- 



* Experiences et remarques critiques sur les sensations des Insectes, Recueil 

 Zdol. Suisse. T. 4, 188fi. 

 t On the Instincts and Senses of Animals. 

 X Popular Science Monthly, vol. xxiii, p. 284. 



