ANATOMY AND PHYSIOLOGY 1 03 



Among beetles, males of Polyphylla gather and scratch at 

 places where females are about to emerge from the ground. 

 Prionus also assembles, as Mrs. Dimmock observed in Massa- 

 chusetts. In this instance many males, with palpitating an- 

 tennae, ran and flew to the female ; moreover, a number of 

 females were attracted to the scene. 



Sounds of Insects. Before considering the sense of hear- 

 ing, some account of the sounds of insects is desirable. Most 

 of these are made by the vibrations of a membrane or by the 

 friction of one part against another. 



The wings of many Diptera and Hymenoptera vibrate with 

 sufficient speed and regularity to give a definite note. The 

 wing tone of a honey bee is A' and that of a common house 

 fly is F'. From the pitch the number of vibrations may be 

 determined; thus A' means 44O 1 vibrations per second and 

 F 1 ', 352. The numbers thus ascertained may be verified by 

 Marey's graphic method (Fig. 74) ; he found that the fly 

 referred to actually made 330 strokes per second against the 

 smoked surface of a revolving cylinder. 



Flies, bees, dragon flies and some beetles make buzzing or 

 humming sounds by means of the spiracles, there being behind 

 each spiracle, a membrane or chitinous projection which vi- 

 brates during respiration. This " voice " should be distin- 

 guished from the wing tone when both are present, as in bees 

 and flies. A fly will buzz when held by the wings, and some 

 gnats continue to buzz after losing wings, legs and head. 

 The wing tone is the more constant of the two; in the honey 

 bee it is A 1 ', falling to E' if the insect is tired, while the spirac- 

 ular tone of the same insect is at least an octave higher (A"} 

 and often rises to B" or C", according to the state of the ner- 

 vous system; in fact, it is possible and even probable that vari- 

 ous spiracular tones express different emotions, as is indicated 

 by the effects produced by the voice of the old queen bee upon 

 the young queens and the males. 



1 Upon the basis of C as 264 vibrations per second. The C of the 

 physicist has 256 as its frequency of vibration. 



