116 Psyche [June 



by them are made solely by the wings, either by their vibration 

 in the air or by striking the wing bases against the body wall. 



In all the experiments I have kept constantly in mind Landois's 

 theory and all my experiments have been performed in an attempt 

 to verify it. However, not in a single instance have the results 

 pointed in any way toward Landois's conclusions. 



The following are the experiments and observations made on 

 Eristalis tenax, similar ones with similar results having been made 

 on several other Diptera and Hymenoptera. 



Experiment I. 



A fresh, living adult was held by the legs allowing free motion 

 with the wings. Two sounds were produced, one low when the 

 insect attempted to fly, and which was made simply by the vibra- 

 tion of the wings in the air, and the other about an octave higher, 

 which was produced when the fly held the wings in a resting posi- 

 tion and vibrated or trembled them very rapidly. This high- 

 pitched note was made by the striking of the wing-bases against 

 the body-wall immediately below and of the wing-bases. A proof 

 for this was given when the wings were cut off close to the 

 bases and the same pitch of note was sounded. A paper strip 

 placed against the tips of the trembling wings so as to act as a 

 sounder, increased the strength of the note which the wing-bases 

 produced. 



Experiment II. 



The wings were cut off close to the body and the insect held by 

 the legs as before. A loud, high-pitched buzz was produced. 

 While producing the sound the wing-stubs were seen to be vibrat- 

 ing rapidly. Upon examining the spiracles while the sound was 

 given, no external activity could be seen about them either in the 

 hairs surrounding the opening or in the normal appearance of the 

 spiracles while the insect was quiet. When a needle was placed 

 against the vibrating wing-stubs the sound always ceased. By 

 cementing the wing-stubs to the body no sound was made, though 

 the spiracles were open and untouched. 



Thus if the fly produces this high-pitched note by means of the 

 spiracles it must be done only when the wings or wing muscles 

 are free to act. 



