248 AN INTRODUCTION TO ZOOLOGY 



138, ho.) supposed to be the end organs of hearing. Each pit 

 has a cone at its base connected with a sensory cell. It is very 

 doubtful, however, whether bees have any sense of hearing, 

 since the exact functions of antennal organs is not known in 

 any case. 



The sounds made by bees may be entirely incidental to 

 other activities. Sounds result from the vibration of the wings, 

 the vibration of the abdominal segments, and the activity of 

 the spiracular vocal apparatus. The size of the wings and 

 physiological condition of the bee determine the rate of vibra- 

 tion, and consequently the pitch. When in full flight, the 440 

 vibrations per second give a in the treble clef, but, if fatigued, 

 only 330 vibrations per second may be produced, giving e. The 

 so-called vocal apparatus lies within the spiracular openings 

 of the respiratory system. It consists of a vocal membrane, 

 a sounding box, and a mechanism for regulating the size of the 

 opening. Air passing to the outside vibrates the membrane 

 producing a humming sound. 



TOUCH. Bees possess a tactile sense, the end organs of which 

 are hairlike structures on various parts of the body, but especially 

 on the antennae. At least two kinds of tactile organs occur on 

 the antennas. One of these consists of a small hair (Fig. 138, /) 

 which projects through a minute opening in the ch'.tin, and is 

 connected with a nerve cell (n) within. The other touch 

 organs are termed conoid hairs (Fig. 138, c'); they are larger, 

 and have a central cavity containing a nerve fiber. More 

 tactile hairs are present near the ends of the antennae than 

 elsewhere. 



The Reproductive System. MALE REPRODUCTIVE ORGANS 

 (Fig. 141). In the abdomen of the drone are two testes (Tes.), 

 each consisting of about three hundred spermatic tubes in which 

 the spermatozoa are formed; they are connected by a pair of fine 

 tubes, the vasa defer entia (V. Def.), with the seminal vesicles (Ves.). 

 The seminal vesicles open into a pair of large mucous glands 

 ?.), which unite at the point where the ejaculatory duct (Ej.D.) 



