648 PROCP^EDIXGS OF THE. ACADEMY OF [Scpt., 



The observations and experiments recorded on the preceding pages 

 lead us to conclude that ants are insensitive to air vibrations, such as 

 are audible to us, and that they are ver}^ sensitive to the vibration of 

 the solid material upon which they stand, be this wood, glass, sponge 

 or the earth of their nests. These vibrations apparently affect their 

 whole bodies, reaching them through their legs or any other part in 

 contact with the solid base. It is of course conceivable that if an 

 air vibration were strong enough — i.e., if the sound were loud 

 enough — it might stimulate the body of the ant directly, but ap- 

 parently this is not usually the case; for, as we have already shown, 

 sounds of ordinary intensity, which call forth no response from the 

 ants when they reach , these animals through the air, are very 

 effective as stimuli when they reach the animal from a solid 

 base. It therefore seems probable to us that ants in their nests are 

 stimulated, not by the sound waves in the air of the nest, but by the 

 vibrations of the solid parts of the nest itself. Hence the effectiveness 

 of a heavy footstep in the neighborhood of an anthill as contrasted with 

 the ineffectiveness of the human voice in causing an active emergence 

 of the ants. These animals are, as it were, in the condition of a per- 

 fectly deaf person who feels through his feet the vibrations caused by 

 a passing wagon, but cannot hear the sound it produces in the air. 

 This sensitiveness of the ants to the \dbrations of the base upon which 

 they rest and their insensitiveness to air vibrations is exactly what 

 would be expected from the requirements of their subterranean life 

 as contrasted with that of aerial insects. 



Because of the analogy between the ants and a deaf person we do 

 not wish, however, to be understood to deny hearing to ants; neither 

 do we affirm it. 



It has long been recognized by physiologists, if not by the scientific 

 public, that touch and hearing in the vertebrates are very closely 

 related. The apparent separateness of these senses in us is due to 

 the fact that the air waves by which our ears are usually stimulated 

 are too slight to affect our organs of touch. If, however, we transfer 

 our experiments to water, we at once meet with a medium in which, 

 as has long been known, vibrations can be both heard and felt. In 

 dealing with a like question among the lower animals it therefore seems 

 to us misleading to attempt to distinguish touch from hearing, and we 

 shall be more within the bounds of accuracy if we discuss the question 

 from the standpoint of mechanical stimulation rather than attempt 

 to set up questionable distinctions based upon human sensations. 

 We therefore prefer to ignore the question of hearing in ants and to 



