1904.] NATURAL SCIENCES OF PHILADELPHIA. 649 



restate our conclusion in the form already given, that these animals are 

 insensitive to the ordinary vibrations of air, but are very sensitive to 

 the vibrations of the solid upon which they stand. 



It seems to us probable from our experiments that the material 

 vibrations that stimulate ants reach them in this way rather than 

 through the air. Janet (1893; 1896, p. 19) has described an ingenious 

 method whereby the stridulating of ants can be heard by the human 

 ear, and Wheeler (1903, p. 66) has been able to note a faint sound when 

 a large number of stridulating ants are collected in a bottle. Undoubt- 

 edly these stridulations are of ecologic importance to an ant community, 

 but it is our belief, based upon our experiments, that what can be heard 

 by the human car through the air is probably not the vibration that 

 affects the ants, but rather that the stridulation produces a vibration 

 of the solid constituents of the nest, and that this vibration is the 

 effective one in stimulating the inmates. 



Summary. 



1. The ants experimented upon did not react to aerial sound waves 

 from a piano, ^dolin, and Galton whistle, which collectively gave a range 

 from 27 to 60,000 vibrations per second. 



2. They reacted to most vibrations that reached them through the 

 wood, glass, sponge or nest-earth upon which they stood, though 

 different species seem to have different superior limits in respect to the 

 rate of the \dbrations. 



3. These reactions are not dependent upon the funicles, the antennae^ 

 the head, the abdomen, any pair or two pairs of legs of the ant, but are 

 usually received through the legs, and probably affect the body of the 

 ant as a whole. 



4. The stimulation of ants by the vibration of the solid upon which 

 they stand, and not by the vibration of the surrounding air, accords 

 well with their subterranean life as contrasted with the aerial life of 

 most insects. 



5. It is misleading to ascribe or deny hearing to ants; they are very 

 sensitive to the vibration of solids, not to those of air; their reactions 

 could be as appropriately described as resulting from touch as from 

 hearing. 



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