THE STRUCTURES CONCERNED. 



The tibia and the planta of the hind leg of the worker bee are 

 greatly flattened. (See figs. 3, 4.) The outer surface of the tibia is 

 marked by an elongated depression, deepest at its distal end, and 

 bounded laterally by elevated margins. From the lateral boundaries 

 of this depression spring many long hairs, some of which arch over 

 the concave outer surface of the tibia and thus form a kind of recep- 

 tacle or basket to which the name corbicula or pollen-basket is given. 

 The lower or distal end of the tibia articulates at its anterior edge with 

 the planta. The remaining portion of this end of the tibia is flat- 

 tened and slightly concave, its 



—Coxa 



%^^— Trochanter 



-Spur 



--■^/rnh onFlanfa 



surface sloping upward from 

 the inner to the outer surface 

 of the limb. Along the inner 

 edge of this surface runs a row 

 of short, stiif, backwardly di- 

 rected spines, from 15 to 21 in 

 number, which form the pec- 

 ten or comb of the tibia. The 

 lateral edge of this area forms 

 the lower boundary of the 

 corbicular depression and is 

 marked by a row of very fine 

 hairs which branch at their 

 free ends. Immediately above 

 these hairs, springing from the 

 floor of the corbicula, are found 

 7 or 8 minute spines, and above 

 them one long hair which 

 reaches out over the lower edge 

 of the basket. 



The broad, flat planta (meta- 

 tarsus or proximal tarsal seg- 

 ment of the hind leg) is marked 

 'on its inner surface by several 

 rows of stiff, distally directed 

 spines wdiich form the pollen 

 combs. About 12 of these transverse rows may be distinguished, 

 although some of them are not complete. The most distal row, which 

 projects beyond the edge of the planta, is composed of very strong, 

 stiff spines which function in the removal of the wax scales (Casteel, 

 1912) . The upper or proximal end of the planta is flattened and pro- 

 jects in a posterior direction to form the auricle. The surface of the 

 auricle is marked with short, blunt spines, pyramidal in form, and a 

 fringe of fine hairs with branching ends extends along its lateral edge. 

 This surface slopes upward and outward. 

 61799°— Bull. 121—12 2 



Pio. 2. 



-Left middle leg of a worker bee. 

 (Original.) 



