66 Annals Entomological Society of America [Vol. X, 



Graber discovered that chordotonal organs are seldom, if 

 ever, found singly, but usually in groups of two to two hundred 

 or more to a system. He discovered that they are located 

 between two immovable points, usually near the body-wall, 

 free from the movements of the inner organs. 



He found them in various species of Orthoptera, Neuoptera, 

 Hemiptera, Coleoptera, Lepidoptera, Diptera and Hymenoptera. 

 They were not always in the same region of the body, but rather 

 often variously located in the different groups. He observed 

 them in the segments of the abdomen, in the antennae of larvae, 

 in the legs and tarsi, in the halteres, in fore wings and the 

 subcostal veins of hind wings. His extended observations led 

 him to believe that the whole integument of insects, like the 

 tympanum of vertebrates, is especially suited to be set into 

 vibration by sounds, and that the nervous structures united to 

 them can react to different sound waves. 



Of the larvae in which Graber reported finding these struc- 

 tures were: Dytiscus among the Coleoptera; Tabanus, Chiron- 

 omus, Tanypus, and Syrphus among the Diptera; and Nematus 

 among the Hymenoptera. His descriptions of these larval 

 structures are very suggestive of what I have found in the 

 abdomen of the Cerambycids. 



From his rather extensive study of widely separated forms, 

 Graber concluded that these organs, though often different in 

 shape, w^ere all alike in essential details. He noticed that the 

 nerve end-organ had three nuclei, but it remained for a later 

 worker to discover the exact relation between the parts of the 

 structure itself. 



Schwabe (190G) in his work on the Locustidas, first showed 

 that the nerve end-organ or scolopophore is composed of three 

 cells with definite cell boundaries. These are: a cap cell, which 

 is often elongated and attached to the body wall; a central 

 portion or enveloping cell; and the sense cell which bears the 

 nerve. 



Schwabe' s results have been largely confirmed by Schon 

 (1910), Vogel (1912), and Lehr (1914). 



