5 '4 ./ATS. 



still closer, whcrea> the smallest workers and minims, though stridu- 

 lating, as may be ,-een from the movements of the gaster on the post- 

 petiole, are quite inaudible to the human ear. It is not at all improb- 

 able that all this differentiation in pitch, correlated as it is with a 

 differentiation in the size and functions of the various members of 

 the colony. i> a very important factor in the cooperation of these insects 

 and of ants in general. The contact-odor sense, important as it 

 undoubtidlv is, must obviously have its limitations in the dark, subter- 

 ranean caxities in which the ants spend so much of their time, espe* 

 cially when the nests are very extensive like those of .Itta. I'nder 

 such conditions stridulation and hearing must be of great service in 

 maintaining the integrity of the colony and of its excavations." If 

 the view of Miss Fielde and Parker be accepted, we must suppose that 

 the J'i></iioin\'rnic.r in the experiment above described, were thrown 

 into agitation by vibrations passing from the bottle of stridulating ants 

 through my body to the soil of the nest. It seems to me much 

 more probable that the ants perceived the stridulation directly as 

 aerial vibrations. More numerous experiments, however, have been 

 recently performed by Turner (1907/7). Although he worked only 

 with Camponotine ants (Formica fusca and F. songiiinca), which 

 are not known to stridulate, he found that they responded to vibra- 

 tions as low as 256 and as high as 4,138 per second. 'The re- 

 sponses, in the form of zigzag movements, were usually slight 

 for pitches higher than 3,000 vibrations per second and sometimes 

 slight for other pitches; but, to most pitches under 3,000 vibrations 

 per second, the ants usually responded in a pronounced manner, usually 

 darting about as though much excited." Turner believes that he took 

 sufficient precautions, by resting the nest on cotton and felt, to exclude 

 the transfer to the ants of vibrations through the floor, table and walls 

 of the nest. It is, however, extremely difficult to prove that such 

 vibrations were excluded, and for this reason we cannot, with the data 

 at hand, reject the statements of Miss Fielde and Parker. As these 

 authors say: "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 senses are usually stimu- 

 lated 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 



