OF THE CULEX MOSQUITO. lOl 



same numbei' of pieces, are very unlike. In the female they 

 are extremely short, but in the male attain the len2:th of 

 2'73mm. ; while the proboscis measures but 2*16 mm. 

 They are curved upwards at the extremity. 



If an organ of hearing, similar to that described by Trevir- 

 anus as belonging to the Blatta orientalis, exist in the head 

 of the Mosquito, the tympanum, must be of exquisitely minute 

 proportions, because the head, which has a diameter of only 

 0' 67 mm., is almost entirely occupied by the corneal plaques, 

 the capsules, and the attachments of the neck and of the 

 buccal apparatus. The membrana tympani must therefore 

 be so small as to preclude the idea of its being put in vibra- 

 tion by any sounds other than those infinitely more acute 

 than are produced by the insect itself, and the use of such an 

 organ for the purposes of inter-communication must be highly 

 problematical. But no trace of such a disposition is to be 

 found in the head, nor very certainly, also, in the body ; and 

 we are obliged to look for some organ which may answer the 

 requirements of an effective auditory apparatus. 



The position of the capsules strikes us as extremely favour- 

 able for the performance of the function which we assign to 

 them ; besides which there present themselves in the same 

 light the anatomical arrangement of the capsules, the disposi- 

 tion and lodgment of tlie nerves, the fitness of the expanded 

 whorls for receiving, and of the jointed antennae fixed by the 

 immovable basal joint for transmitting vibrations created by 

 sonorous modulations. The intra-capsular fluid is impressed 

 by the shock, the expanded nerve appreciates the effect of the 

 sound, and the animal may judge of t!ie intensity, or distance, 

 of the source of sound, by the quantity of the impression : of 

 the pitch, or quality, by the consonance of particular whorls 

 of the stiff hairs, according to their lengths ; and of the direc- 

 tion in which the modulations travel, by the manner in which 

 they strike upon the antenna, or may be made to meet either 

 antenna, in consequence of an opposite movement of that part. 



That the male should be endowed with superior acuteness 

 of the sense of hearing appears from tlie fact, that he must 

 seek the female for sexual union either in the dim twili"-ht 

 or in the dark night, when nothing save her sharp humming 

 noise can serve him as a guide. The necessity for an equal 

 perfection of hearing does not exist in the female ; and, 

 accordingly, we find that the organs of the one attain to a 

 development which the others never reach. In these views 

 we believe ourselves to be borne out by direct experiment, 

 in connexion with which we may allude to the greater diffi- 

 culty of catching the male Mosquito. 



