THE STRUCTURES CONCERNED IN THE MANIPULATION OF POLLEN.
The hairs which cover the body and appendages of the bee are of the utmost importance in the process of pollen gathering. For the purposes of this account these hairs may be classified roughly as (1) branched hairs and (2) unbranched hairs, the latter including both long, slender hairs and stiff, spinelike structures.
Of these two classes the branched hairs are the more numerous. They make up the hairy coat of the head, thorax, and abdomen, with the exception of short sensory spines, as those found upon the antennæ and perhaps elsewhere, and the stiff unbranched hairs which cover the surfaces of the compound eyes (Phillips, 1905). Branched hairs are also found upon the legs; more particularly upon the more proximal segments. A typical branched hair is composed of a long slender main axis from which spring numerous short lateral barbs.
Grains of pollen are caught and held in the angles between the axis and the barbs and between the barbs of contiguous hairs. The hairy covering of the body and legs thus serves as a collecting surface upon which pollen grains are temporarily retained and from which they are later removed by the combing action of the brushes of the legs. Although, as above noted, some unbranched hairs are located upon the body of the bee, they occur in greatest numbers upon the more distal segments of the appendages. They are quite diverse in form, some being extremely long and slender, such as those which curve over the pollen baskets, others being stout and stiff, as those which form the collecting brushes and the pecten spines.
The mouthparts of the bee are also essential to the proper collection of pollen. The mandibles are used to scrape over the anthers of flowers, and considerable pollen adheres to them and is later removed. The same is true of the maxillæ and tongue. From the mouth comes the fluid by which the pollen grains are moistened.
The legs of the worker bee are especially adapted for pollen gathering. Each leg bears a collecting brush, composed of stiff, unbranched hairs set closely together. These brushes are located upon the first or most proximal tarsal segment of the legs, known technically as the palmæ of the forelegs and as the plantæ of the middle and hind pair. The brush of the foreleg is elongated and of slight width, that of the middle leg broad and flat, while the brush upon the planta of the hind leg is the broadest of all, and is also the most highly specialized. In addition to these well-marked brushes, the distal ends of the tibiæ of the fore and middle legs bear many stiff hairs, which function as pollen collectors, and the distal tarsal joints of all legs bear similar structures.
The tibia and the planta of the hind leg of the worker bee are greatly flattened. 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 receptacle 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 flattened and slightly concave, its 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 directed spines, from 15 to 21 in number, which form the pecten or comb of the tibia. The lateral edge of this area forms the lower boundary of the corbicula r 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 (metatarsus or proximal tarsal segment 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 projects 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.
Source: The Behavior of the Honey Bee in Pollen Collection, by D. B. Casteel (University of Texas.). This work is dutifully reproduced under Public Domain law from the eBook release on Project Gutenberg. Text remains verbatim with permissible edits to paragraph formatting and inclusion of relevant URLs.