68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



name has been used for the antenna cleaner ; the brush serves for 

 the collection and retention of pollen to be stored in the pollen basket 

 of the tibia. The deep notch in the dorsal margin of the hind leg 

 between the tibia and the basitarsus is converted in the worker into a 

 pollen press for the transfer of pollen from the basitarsal brush of one 

 leg into the tibial basket of the other. 



The pollen press of the worker bee is a simple adaptation of the 

 pincerlike tibio-tarsal notch for pushing pollen from one side of the 

 leg to the other and for compressing it in the pollen basket. The 

 proximal end-surface of the basitarsus opposed to the distal end of 

 the tibia (fig. 23 B) is beveled outward and upward toward the 

 tibia and is expanded in a small lobe, known as the auricle (au), 

 bordered by a fringe of long hairs. The surface of the auricle is 

 covered with small spicules, and is limited mesally by a strong ridge. 

 The opposing free end of the tibia bears mesally a row of short, 

 closely set, sinuous spines, forming a little rake, or rastellmn {ras), 

 which projects down over the base of the auricle (D, E). Laterad 

 of the rastellum the end-surface of the tibia is concave and is sepa- 

 rated by a low ridge from the floor of the pollen basket above it on 

 the outer (anterior) surface of the tibia (C, chl). When the basi- 

 tarsus is bent upward at the tibio-tarsal joint (D, E), the fringed lip 

 of the auricle, guarded mesally by the rastellum, passes within the 

 semicircle of long curved hairs on the lower end of the tibia and over- 

 laps the floor of the pollen basket. As this gadget is used by the 

 bee for loading the pollen basket, a small mass of pollen is first 

 raked ofif from the basitarsal brush of the opposite leg by the rastellum 

 of the tibia; the detached pollen falls on the rough surface of the 

 auricle and adheres to it. Then, by an upward flexure of the tarsus 

 on the tibia, the mass of pollen on the auricle, held in place by the 

 rastellum, is pressed up into the tibial basket. With repeated scrapings 

 and operations of the press the basket is finally loaded by successive 

 increments of pollen added at the bottom of the mass. 



It is interesting to note that both the antenna cleaner and the pollen 

 press are developed at the tibio-tarsal joint. This joint differs from 

 the other leg joints in that the tarsus has a monocondylic hinge on the 

 tibia, and three muscles. Since this structure pertains to the cor- 

 responding joint in all the legs of the three castes of the bee, it is 

 clear that it is not an adaptation to either the antenna cleaner or the 

 pollen press. On the other hand, it is possible that the development 

 of these instruments has depended on the peculiar nature of the tibio- 

 tarsal joint and the unusual mobility of the tarsus. 



