1917] Chordotonal Organs of Cerambycid Larvce 65 



According to Graber, details of the auditory organ of insects 

 were first described by John Miiller (1826). Miiller discovered 

 a structure in the tympanum of the Acrididas, which he described 

 as an elongated bubble filled with water, one end fastened to the 

 tympanic membrane, the other end extending in the opposite 

 direction. 



Siebold (1844) found in the fore tibia of the Locustidae, a 

 ganglion-like body which ended in the form of a band at the 

 side of a large trachea, and which was composed of rod-shaped 

 little bodies. Some later writers attribute the discovery of the 

 auditory nerve end-organ, or scolopophore, to this worker. 



Ley dig (1851) found in the larva of Corethra plumicornis, 

 nerve endings which were located in the segments of the 

 abdomen. They were attached at each end to the skin, and 

 stretched lengthwise across the clear space located between the 

 body wall and the muscles. In 1860 Leydig farther investigated 

 the adults and larv^ of Diptera and Coleoptera, and demon- 

 strated the peculiar nerve end apparatus. He described these 

 structures in the antennae, halteres, and wings, but did no 

 farther work on the abdominal organs. His is the first clear 

 description we find of these nerve end bodies, and as a result 

 Leydig is given credit for discovering them. 



Weismann (1866) found in Corethra plumicornis, little nerve 

 endings which he called "cords of hearing." He maintained 

 that this hearing cord was very suitable to be set into vibration 

 by sound waves. 



Hensen (1866) showed that in the Locustidae, the nerve 

 fibers of the auditory nerve join the auditory rod or scolopale. 

 Schmidt (1875) largely confirmed the work of Hensen, but 

 discovered that the nerve fiber extended from a basal ganglion 

 cell into the scolopale. 



Although the workers mentioned above contributed con- 

 siderable to our knowledge of these sense organs, the work of 

 Graber (1881-82) laid the foundation for all future work. This 

 worker called chordotonal, all organs that had nerve endings 

 similar to those of the previously described auditory rods of the 

 Orthoptera, and maintained that such organs serve an auditory 

 function. He supported this view by showing that chordotonal 

 organs in the various orders of insects all contain peg-like bodies 

 or scolopalae, such as are found in the tympanal organs of the 

 Orthoptera. 



