110 THE PHYSIOLOGY OF INSECT SENSES 



by means of disturbances in the blood, the argument that it is necessary 

 in order to permit the organ to respond to higher stimulus frequencies 

 is not valid. For example, alternation of firing in the various fibres, as 

 in the cereal hairs, would accomplish the same purpose. 



5 10 



100 



300 400 



4000 6000 8.000 



600 800 1000 1.500 2,000 2.500 



Cycles per Second 



Fig. 70. Comparisons of the vibration thresholds of flies (O 



men (O O), bullfinches (• •), bees (• • ) 



cockroaches (C €). (Redrawn from Schneider, 1950.) 



•O), 

 and 



Those who would consider sensitivity to vibrations in solids a 

 separate sense, compare the abilities of man, birds, and insects (the 

 only animals for which threshold values are known) in this respect and 

 find insects to be the most as well as the least sensitive. The cockroach 

 at its optimum range is more sensitive by a factor of 10,000 than the 



