72 Annals Entomological Society of America [Vol. X, 



Authors disagree regarding the function of these organs. 

 Graber ('82), Schwabe ('06), Schon ('10), and many others 

 regard them as organs of hearing, but some of the more recent 

 writers, such as Radl ('05) maintain that they have a static 

 function. 



No muscles were found which appeared to function in 

 regulating the length of the ligaments, and it seems, so far as 

 could be discerned, that the length is constant. \n the Corethra 

 larva these ligaments have been observed to shorten and 

 lengthen in the living animal, but from a study of the chordo- 

 tonal ligaments in the wood-boring Cerambycid larvae, it does 

 not seem possible that their length is changeable. 



The external covering of the chordotonal ligament is rather 

 thick, due largely to the fact that the basement membrane 

 which covers the hypodermis internally, also forms a covering 

 about this structure. 



What relation the tracheal system has to these organs is not 

 certain. Schwabe ('06) found enlarged tracheal sacks in the 

 region of the organs in the Orthoptera. Vogel ('12) found a 

 corresponding relation between the chordotonal organs in the 

 wings of butterflies and the trachea. Lehr ('14) found a similar 

 condition in the wings of Dystiscus marginalis. In the abdomen 

 of the forms here studied, a rather large trachea was always 

 observed in close apposition to that part of the chordotonal 

 ligaments which contained the peg-shaped bodies or scolopal^. 



The cuticula at the posterior point of attachment of the 

 chordotonal ligaments in all species studied, and at both ends in 

 Monohammus confusor, was found modified into a very hard, 

 dark-staining structure. This condition, together with the 

 arrangement of the scolopalas in the ligaments, seems to favor 

 the idea that the organs are for hearing, rather than for bal- 

 ancing, since sound waves could easily be transferred by this 

 hardened cuticula to the ligament, which by its vibration, could 

 carry the impulse to the nerve and organ. 



