THE STRUCTURES CONCERNED. 
9 
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 
-Femur 
-Brush on Planta 
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, stiff, 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 which 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 
Fig. 2. 
-Left middle leg of a worker bee. 
( Original. ) 
