38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 5 1 



E. Weinland (Zeitschr. f. Wissens. Zool., li. pp. 55-166) lias con- 

 cluded from his studies of the halteres that these organs are func- 

 tional in determining the direction of flight. They can he used to 

 steer a course in the vertical plane as well as in other directions, 

 lie also concluded that the chordotonal structures in the hase of the 

 halteres allow the perception of the steering movements of these 

 organs. But it is highly probable that the great nerve trunk sup- 

 plied to the halter is not primarily subservient to this dirigible func- 

 tion, hut rather to that of audition, at least in the higher families. 

 In the Nemocera the halteres may be mainly dirigible or equilibratory 

 in function, since the auditor}' organs are located in the antenna?. 

 In the Cyclorrhapha, however, it seems safe to assume that their 

 function is primarily auditory. As Lowne suggests, the halteres are 

 doubtless microphones of a most efficient nature, capable of perceiv- 

 ing sound waves of such low intensity that they do not affect the 

 vertebrate car. They possess a function of coordination, similar to 

 that of the semicircular canals of vertebrates, and thus arc organs 

 combining the functions of equilibration and audition. 



The tegulse of the Schizometopa and some other Diptera are very 

 likely functional in collecting sound-waves, increasing the perceptive 

 power of the chordotonal organs of the halteres, thus being ana- 

 logues of the external cartilaginous ear-lobes of the mammalia. 

 They also doubtless serve secondarily as a protection to the highly 

 sensory halteres. It seems .safe to assume that in those dipterous 

 groups having no tegular the halteres perform chiefly a function of 

 equilibration, but that in those groups furnished with tegulse the hal- 

 teres are mainly organs of audition. In other words, the presence of 

 well-developed tegulse indicate- the presence of a highly developed 

 auditory sense in the halteres. Mere protection to the latter would 

 not demand such structures as the tegulse, while it can not be denied 

 that they arc admirably adapted to such a function as the collection 

 of sound-waves. 



Whatever may be finally determined as to their functions, it is 

 certain that the habere- are highly specialized organs. The tegulse, 

 without doubt accessory to them, are by inference equally functional 

 and of coincident evolution with some function pertaining to them. 

 The latter, therefore, can not be accepted as affording characters of 

 value for the separation of large groups, but are rather of decidedly 

 inferior rank in this respect to the veins of the wings. They occur 

 in other groups entirely outside of and removed from the Schizo- 

 phora, and even from the Cyclorrhapha. Their presence in the An- 

 thomyioidea is therefore not necessarily to be construed as indicating 

 a close relationship between that superfamily and. the Muscoidea. 



