154 



AN INTRODUCTION TO ENTOMOLOGY 



As to the action of the auditory apparatus as a whole, it was shown 

 experimentally by Mayer ('74) that the different whorls of setas borne 

 by the segments of the clavola, and which gradually decrease in length 

 on successive segments, are caused to vibrate by different notes; and 

 it is believed that the vibrations of the setae are transferred to the 

 conjunctival plate by the clavola, and thence to the nerve-end- 

 ings. 



It was formerly 

 believed that the 

 great specialization 

 of the Johnston's or- 

 gan in male mosqui- 

 toes enabled the 

 males to hear the 

 songs of the females 

 and thus more readily 

 to find their mates. 

 But it has been found 

 that in some species, 

 at least, of mosquitoes 

 and of midges in 



Fig. 174. Longitudinal section of the base of an anten- which the males 



na of a male mosquito, Corethra culiciformis (After -, , * 



Child)< have this organ 



highly specialized the 



females seek the males. This has led some writers to doubt that the 

 Johnston's organ is auditory in function. But the fact remains that 

 its distinctive feature is the presence of scolopalae, which is the dis- 

 tinctive characteristic of the auditory organs of other insects. 



N 



XIV. SENSE-ORGANS OF UNKNOWN FUNCTIONS 



In addition to the sense-organs discussed in the foregoing account 

 there have been described several types of supposed sense-organs 

 which are as yet very imperfectly understood. Among these there is 

 one that merits a brief discussion here on account of the frequent 

 references to it in entomological literature. Many different names 

 have been applied to the organs of this type; of these that of sense- 

 domes is as appropriate as any, unless the conclusions of Mclndoo, 

 referred to below, are confirmed, in which case his term olfactory pores 

 will be more descriptive. 



