IgQ N. E. McINDOO 



the only olfactory pores on the antenna of the honey-bee. The 

 external and internal structure (fig. 8) are Uke those already 

 described by the writer ('14 a). i i j 



b. Structure of pore plates. The pore plates or sensiUa placodea, 

 according to the writer's discussion of the antennal organs ('14 b), 

 were first studied in 1847 by Erichson, who caUed them olfactory 

 organs. Since this date they have been studied by about three 

 dozen other investigators whose views concerning their function 

 differ widely. In 1851 Vogt suggested that they perform a func- 

 tion combining those of smell and touch. In 1858 Lespes com- 

 pared them to the ears of higher animals, and a year later Hicks 

 called them auditory organs. Practically all of the other authors 

 up to 1888, who have studied the pore plates, regard them as 

 olfactory organs. Ruland ('88), after having boiled antennae in 

 caustic potash, saw that a pore plate is suspended on a membrane, 

 resembling a double hinge, similar to that observed in sections 

 stained in eosin by the present writer. Owing to this arrange- 

 ment, he called them auditory organs. In 1894 Nagel favored 

 the olfactory view, but also thought that the pore plates might 

 have a inechanical function. He suggested that air pressure 

 might affect them. Nine years later Schenk ('03) stated, that the 

 thick plates in these organs eliminated the possibility of these 

 structures being olfactory organs, but judging from their anatomy 

 he regarded them as having a mechanical function. He favors 

 the view that they are pressure points to inform the bee of the 

 object immediately in front of it. 



According to Schenk's calculations, a male honey-bee has 

 31,356 pore plates and a female has only 3,648. According to 

 the calculations of the present writer, a drone on an average has 

 ■29,718 pore plates; a worker has 4,744, and a queen has 2,776, 

 Those of the drone are much smaller than those of the worker 

 or queen, but supposing that their sensitiveness is in direct pro- 

 portion to the total area of all their plates, then if the sensitive- 

 ness of those on a worker equals 1, that of those on a drone equals 

 3, and that of those on a queen equals only 0.6. These organs 

 (fig. 3, P) are found only on the fifth to twelfth antennal segments 

 of the worker and queen, and on the fifth to thirteenth segments 



