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Behavior of the Honey Bee in Pollen Collecting, The

U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY—BULLETIN No. 121. L. O. HOWARD. Entomologist and Chief of Bureau. <hr class="r10" /> THE BEHAVIOR OF THE HONEY BEE IN POLLEN COLLECTING. BY D. B. CASTEEL, Ph. D., Collaborator and Adjunct Professor of Zoology, University of Texas. Issued December 31, 1912. <div class="fig_center pmt2 pmb2"> <ANTIMG src="images/pg_1_logo.png" width-obs="225" height-obs="223" alt="" title="" /></div> WASHINGTON: GOVERNMENT PRINTING OFFICE. 1912. BUREAU OF ENTOMOLOGY. L. O. Howard, Entomologist and Chief of Bureau. C. L. Marlatt, Entomologist and Acting Chief in Absence of Chief. R. S. Clifton, Executive Assistant. W. F. Tastet, Chief Clerk. F. H. Chittenden, in charge of truck crop and stored product insect investigations. A. D. Hopkins, in charge of forest insect investigations. W. D. Hunter, in charge of southern field crop insect investigations. F. M. Webster, in charge of cereal and forage insect investigations. A. L. Quaintance, in charge of deciduous fruit insect investigations. E. F. Phillips, in charge of bee culture. D. M. Rogers, in charge of preventing spread of moths, field work. Rolla P. Currie, in charge of editorial work. Mabel Colcord, in charge of library. Investigations in Bee Culture. E. F. Phillips, in charge. G. F. White, J. A. Nelson, experts. G. S. Demuth, A. H. McCray, N. E. McIndoo, apicultural assistants. Pearle H. Garrison, preparator. D. B. Casteel, collaborator. LETTER OF TRANSMITTAL. U. S. Department of Agriculture,        Bureau of Entomology,    Washington, D. C, September 23, 1912. Sir: I have the honor to transmit herewith a manuscript entitled "The Behavior of the Honey Bee in Pollen Collecting," by Dr. Dana B. Casteel, of this bureau. The value of the honey bee in cross pollinating the flowers of fruit trees makes it desirable that exact information be available concerning the actions of the bee when gathering and manipulating the pollen. The results recorded in this manuscript are also of value as studies in the behavior of the bee and will prove interesting and valuable to the bee keeper. The work here recorded was done by Dr. Casteel during the summers of 1911 and 1912 at the apiary of this bureau. I recommend that this manuscript be published as Bulletin No. 121 of the Bureau of Entomology.     Respectfully, L. O. Howard,    Entomologist and Chief of Bureau. Hon. James Wilson, Secretary of Agriculture. CONTENTS. <table style="width:100%" summary="ToC"> <tr> <td></td> <td class="tdr">Page.</td> </tr> <tr> <td>Introduction</td> <td class="tdr">7</td> </tr> <tr> <td>The structures concerned in the manipulation of pollen</td> <td class="tdr">7</td> </tr> <tr> <td>The pollen supply</td> <td class="tdr">10</td> </tr> <tr> <td>General statement of the pollen-collecting process</td> <td class="tdr">11</td> </tr> <tr> <td>Action of the forelegs and mouthparts</td> <td class="tdr">13</td> </tr> <tr> <td>Action of the middle legs</td> <td class="tdr">14</td> </tr> <tr> <td>Action of the hind legs</td> <td class="tdr">16</td> </tr> <tr> <td>Additional details of the basket-loading process</td> <td class="tdr">18</td> </tr> <tr> <td>Pollen moistening</td> <td class="tdr">22</td> </tr> <tr> <td>Storing pollen in the hive</td> <td class="tdr">29</td> </tr> <tr> <td>Summary</td> <td class="tdr">31</td> </tr> <tr> <td>Bibliography</td> <td class="tdr">33</td> </tr> <tr> <td>Index</td> <td class="tdr">35</td> </tr> </table> ILLUSTRATIONS. TEXT FIGURES. <table style="width:100%" summary="ToI"> <tr> <td colspan="3"></td> <td class="tdr">Page.</td> </tr> <tr> <td class="vtop" rowspan="9">Fig.</td> <td>1.</td> <td>Left foreleg of a worker bee</td> <td class="tdr">8</td> </tr> <tr> <td>2.</td> <td>Left middle leg of a worker bee</td> <td class="tdr">9</td> </tr> <tr> <td>3.</td> <td>Outer surface of the left hind leg of a worker bee</td> <td class="tdr">10</td> </tr> <tr> <td class="vtop">4.</td> <td>Inner surface of the left hind leg of a worker bee</td> <td class="tdr">11</td> </tr> <tr> <td class="vtop">5.</td> <td>A flying bee, showing the manner in which the forelegs and middle legs manipulate pollen</td> <td class="tdr">14</td> </tr> <tr> <td class="vtop">6.</td> <td>A bee upon the wing, showing the position of the middle legs when they touch and pat down the pollen masses</td> <td class="tdr">15</td> </tr> <tr> <td class="vtop">7.</td> <td>A bee upon the wing, showing the manner in which the hind legs are held during the basket-loading process</td> <td class="tdr">17</td> </tr> <tr> <td class="vtop">8.</td> <td>The left hind legs of worker bees, showing the manner in which pollen enters the basket</td> <td class="tdr">19</td> </tr> <tr> <td class="vtop">9.</td> <td>Inner surface of the right hind leg of a worker bee which bears a complete load of pollen</td> <td class="tdr">22</td> </tr> </table> <h1 class="pmt2 pmb4">THE BEHAVIOR OF THE HONEY BEE IN POLLEN COLLECTING. </h1> <h2>INTRODUCTION.</h2> While working upon the problem of wax-scale manipulation during the summer of 1911 the writer became convinced that the so-called wax shears or pinchers of the worker honey bee have nothing whatever to do with the extraction of the wax scales from their pockets, but rather that they are organs used in loading the pollen from the pollen combs of the hind legs into the corbicul� or pollen baskets (Cast eel, 1912). Further observations made at that time disclosed the exact method by which the hind legs are instrumental in the pollen-loading process and also the way in which the middle legs aid the hind legs in patting down the pollen masses. During the summer of 1912 additional information was secured, more particularly that relating to the manner in which pollen is collected upon the body and legs of the bee, how it is transferred to the hind legs, how it is moistened, and finally the method by which it is stored in the hive for future use. In the present paper a complete account will be given of the history of the pollen from the time it leaves the flower until it rests within the cells of the hive. The points of more particular interest in the description of pollen manipulation refer to (1) the movements concerned in gathering the pollen from the flowers upon the body and legs, (2) the method by which the baskets of the hind legs receive the loads which they carry to the hive, and (3) the manner in which the bee moistens pollen and renders it sufficiently cohesive for packing and transportation. <h2>THE STRUCTURES CONCERNED IN THE MANIPULATION OF POLLEN.</h2> 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 antenn� 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 maxill� 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 palm� of the forelegs and as the plant� of the middle and hind pair. The brush of the foreleg is elongated and of slight width (fig. 1), that of the middle leg broad and flat (fig. 2), 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 tibi� 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. <div class="fig_center" style="width:420px"> <ANTIMG src="images/fig_1.png" width-obs="420" height-obs="333" alt="" title="" /> Fig. 1.—Left foreleg of a worker bee. (Original.) </div> 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 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. <div class="fig_right" style="width: 293px;"> <ANTIMG src="images/fig_2.png" width-obs="293" height-obs="506" alt="" title="" /> Fig. 2.—Left middle leg of a worker bee. (Original.) </div> 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. <div style="break-after:column;"></div>

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