THE DALTEBES AND WING OBQANS. 99 



acetic acid, but the otolitea of molluscs are not affected by 

 prolonged treatment with it.* I further think it extremely 

 probable that the globe of the halter receives the undulations 

 of sound, which are propagated through the fluid to these 

 corpuscles. 



Perhaps in insects not provided with halteres, the wings 

 may receive the undulations of sound upon their whole 

 surface, which are so propagated, probably less perfectly to 

 the organs on the sub-costal nervure, which are very numerous 

 in most genera. 



With regard to the position of the organs, bearing in mind 

 the rapid vibrations to which the integuments of the head 

 and thorax are subject during flight, and more especially during 

 the emission of sound, I conceive that the wings and legs are 

 probably the least agitated parts, and are hence fittest for the de- 

 velopment of auditory organs. During flight, the expansion of 

 the wing must evidently be the steadiest portion of the insect, as 

 it forms the point d'appui upen which it moves. The halteres 

 are certainly not much affected by the vibrations of the body ; 

 they are beautifully balanced by muscles, and are connected 

 only by membranous integument with the flank. 



To conclude this subject : we know the auditory organs of 

 some saltorial Orthoptera are developed on their anterior, 

 femora, and, according to Dr. B. Hicks, the wing organs are 

 absent in the Orthoptera. Much careful work is needed 

 however, in examining these structures in various genera. 



The halteres are developed, like the wings, from a distinct 

 imaginal disc. 



* W. Burnett's Translation of Siebold, Sec. 211, Note ii. 



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