4f. £v/ay 
 
 U. S. DEPARTMENT OF AGRICULTURE, 
 ' BUREAU OF ENTOMOLOGY— BULLETIN No. 121. 
 
 L. O. HOWARD, Entomologist and Chief of Bureau. 
 
 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. 
 
 I 
 
 O^cumSnt^^pt 
 
 
 i 
 
 ..... "*n»r* 
 
 
 
 U.S. DEPOSITORY 
 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 
 1912. 
 
U. S. DEPARTMENT OF AGRICULTURE, 
 BUREAU OF ENTOMOLOGY— BULLETIN No. 121. 
 
 L. O. HOWARD. Entomologist and Chief of Bureau. 
 
 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. 
 
 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. 
 2 
 
LETTER OE 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 pol- 
 linating the flowers of fruit trees makes it desirable that exact infor- 
 mation be available concerning the actions of the bee when gathering 
 and manipulating the pollen. The results recorded in this manu- 
 script 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. 
 
 Page. 
 
 Introduction 7 
 
 The structures concerned in the manipulation of pollen 7 
 
 The pollen supply 10 
 
 General statement of the pollen-collecting process 11 
 
 Action of the forelegs and mouthparts 13 
 
 Action of the middle legs 14 
 
 Action of the hind legs 16 
 
 Additional details of the basket-loading process 18 
 
 Pollen moistening 22 
 
 Storing pollen in the hive 29 
 
 Summary 31 
 
 Bibliography 33 
 
 Index 35 
 
 5 
 
ILLUSTRATIONS. 
 
 TEXT FIGURES. 
 
 Page. 
 Fig. 1. Left foreleg of a worker bee 8 
 
 2. Left middle leg of a worker bee 9 
 
 3. Outer surface of the left hind leg of a worker bee 10 
 
 4. Inner surface of the left hind leg of a worker bee 11 
 
 5. A flying bee, showing the manner in which the forelegs and middle legs 
 
 manipulate pollen 14 
 
 6. A bee upon the wing, showing the position of the middle legs when they 
 
 touch and pat down the pollen masses 15 
 
 7. A bee upon the wing, showing the manner in which the hind legs are 
 
 held during the basket-loading process 17 
 
 8. The left hind legs of worker bees, showing the manner in which pollen 
 
 enters the basket 19 
 
 9. Inner surface of the right hind leg of a worker bee which bears a com- 
 
 plete load of pollen 22 
 
THE BEHAVIOR OF THE HONEY BEE IN POLLEN COLLECTING. 
 
 INTRODUCTION". 
 
 While working upon the problem of wax-scale manipulation dur- 
 ing 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 corbiculse or pollen 
 baskets (Cast eel, 1912). Further observations made at that time dis- 
 closed 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 particu- 
 larly 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 par- 
 ticular 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 suf- 
 ficiently cohesive for packing and transportation. 
 
 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 an- 
 tenna 3 and perhaps elsewhere, and the stiff unbranched hairs which 
 
 7 
 
8 
 
 BEHAVIOR OF HONEY BEE IN POLLEN COLLECTING. 
 
 Trochanter^ 
 
 TMa 
 
 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 jDollen 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 
 JJoxa baskets, others 
 
 being stout and 
 stiff, as those 
 which form the 
 collecting brushes 
 and the pecten 
 spines. 
 
 The mouth- 
 parts of the bee 
 are also essential 
 to the proper col- 
 lection 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 maxillae 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 gath- 
 ering. Each leg bears a collecting brush, composed of stiff, un- 
 branched hairs set closely together. These brushes are located upon 
 the first or most proximal tarsal segment of the legs, known techni- 
 cally as the palmae of the forelegs and as the plantae 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 ajso the most highly specialized. In addition to these well-marked 
 brushes, the distal ends of the tibia? 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. 
 
 Fig. 1. — Left foreleg of a worker bee. (Original.) 
 
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 
 
 -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 
 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 (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. 
 -inal.) 
 
10 
 
 uliiawoi; of honey bee in pollen collecting. 
 
 THE POLLEN SUPPLY. 
 
 When bees collect pollen from flowers they may be engaged in this 
 occupation alone or may combine it with nectar gathering. From 
 some flowers the bees take only nectar, from others only pollen; a 
 
 third class of flowers furnishes 
 an available supply of both of 
 these substances. But even 
 where both pollen and nectar 
 are obtainable a bee may 
 gather nectar and disregard 
 the pollen. This is well illus- 
 trated by the case of white 
 clover. If bees are watched 
 while working upon clover 
 flowers, the observer will soon 
 perceive some which bear pol- 
 len masses upon their hind 
 legs, while others will continue 
 to visit flower after flower, 
 dipping into the blossoms and 
 securing a plentiful supply of 
 nectar, yet entirely neglecting 
 the pollen. 
 
 The supply of pollen which 
 is available for the bees varies 
 greatly among different flow- 
 ers. Some furnish an abun- 
 dant amount and present it to 
 the bee in such a way that 
 little difficulty is experienced 
 in quickly securing an ample 
 load, while others furnish but 
 little. When flowers are small 
 and when the bee approaches 
 them from above, little, if any, 
 pollen is scattered over the 
 bee's body, all that it acquires 
 being first collected upon the 
 mouth and neighboring parts, 
 of a Very different conditions are 
 met with when bees visit such 
 plants as corn and ragweed. The flowers of these plants are pendent 
 and possess an abundant supply of pollen, which falls in showers over 
 the bodies of the bees as they crawl beneath the blossoms. The 
 
 %-Planta 
 
 Pig. ::. 
 
 Outer surface of the left hind le^ 
 worker bee. (Original.) 
 
GENERAL STATEMENT OF PROCESS. 
 
 11 
 
 supply of pollen which lodges upon the body of the bee will thus 
 differ considerably in amount, depending upon the type of flower 
 from which the bee is collecting, and the same is true regarding the 
 location upon the body of a bee of pollen grains which are available 
 for storage in the baskets. 
 Moreover, the movements 
 concerned in the collection 
 of the pollen from the va- 
 rious body parts of the 
 bee upon which it lodges 
 will differ somewhat in 
 the two cases, since a 
 widely scattered supply 
 requires for its collection 
 a ddit ional movements, 
 somewhat similar in na- 
 ture to those which the 
 bee employs in cleaning 
 the hairs which cover its 
 bodv. 
 
 Tibia 
 
 -Anterior 
 edge 
 
 Posternr 
 eage- 
 
 GENERAL STATEMENT 
 OF THE POLLEN-COL- 
 LECTING PROCESS. 
 
 Pecten 
 
 Auricle 
 
 Pollen 
 onPlanfa 
 
 A very complete knowl- 
 edge of the pollen-gather- 
 ing behavior of the worker 
 honey bee may be obtained 
 by a study of the actions 
 of bees which are ' work- 
 ing upon a plant which 
 yields pollen in abun- 
 dance. Sweet corn is an 
 ideal plant for this pur- 
 pose, and it will be used 
 as a basis for the descrip- 
 tion which follows. 
 
 In attempting to out- 
 line the method by which FlG 
 pollen is manipulated the 
 writer wishes it to be understood that he is recounting that which 
 he has seen and that the description is not necessarily complete, 
 although he is of the opinion that it is very nearly so. The move- 
 ments of the legs and of the mouthparts are so rapid and so many 
 
 Inner surface of the left hind leg of a 
 worker bee. (Original ) 
 
12 BEHAVIOR OF HONEY BEE IX POLLEN COLLECTING. 
 
 members are in action at once that it is impossible for the eye to 
 follow all at the same time. However, long-continued observation, 
 assisted by the study of instantaneous photographs, gives confidence 
 that the statements recorded are accurate, although some movements 
 may have escaped notice. 
 
 To obtain pollen from corn the bee must find a tassel in the right 
 stage of ripeness, with flowers open and stamens hanging from them. 
 The bee alights upon a spike and crawls along it, clinging to the 
 pendent anthers. It crawls over the anthers, going from one flower 
 to another along the spike, being all the while busily engaged in the 
 task of obtaining pollen. This reaches its body in several ways. 
 
 As the bee moves over the anthers it uses its mandibles and tongue, 
 biting the anthers and licking them and securing a considerable 
 amount of pollen upon these parts. This pollen becomes moist and 
 sticky, since it is mingled with fluid from the mouth. A considerable 
 amount of pollen is dislodged from the anthers as the bee moves over 
 them. All of the legs receive a supply of this free pollen and much 
 adheres to the hairs which cover the body, more particularly to those 
 upon the ventral surface. This free pollen is dry and powdery and 
 is very different in appearance from the moist pollen masses with 
 which the bee returns to the hive. Before the return journey this 
 pollen must be transferred to the baskets and securely packed in them. 
 
 After the bee has traversed a few flowers along the spike and has 
 become well supplied with free pollen it begins to collect it from its 
 body, head, and forward appendages and to transfer it to the pos- 
 terior pair of legs. This may be accomplished while the bee is 
 resting upon the flower or while it is hovering in the air before 
 seeking additional pollen. It is probably more thoroughly and rap- 
 idly accomplished while the bee is in the air, since all of the legs are 
 then free to function in the gathering process. 
 
 If the collecting bee is seized with forceps and examined after it 
 has crawled over the stamens of a few floAvers of the corn, its legs 
 and the ventral surface of its body are found to be thickly powdered 
 over with pollen. If the bee hovers in the air for a few moments 
 and is then examined very little pollen is found upon the body or 
 upon the legs, except the masses within the pollen baskets. "While in 
 the air it has accomplished the work of collecting some of the scat- 
 tered grains and of storing them in the baskets, while others have 
 been brushed from the body. 
 
 In attempting to describe the movements by which this result is 
 accomplished it will be best first to sketch briefly the roles of the 
 three pairs of legs. They are as follows : 
 
 (a) The first pair of legs remove scattered pollen from the head 
 and the region of the neck, and the pollen that has been moistened 
 by fluid substances from the mouth. 
 
ACTION OF FORELEGS AND MOUTHPARTS. 13 
 
 (b) The second pair of legs remove scattered pollen from the 
 thorax, more particularly from the ventral region, and they re- 
 ceived the pollen that has been collected by the first pair of legs. 
 
 (<?) The third pair of legs collect a little of the scattered pollen 
 from the abdomen and they receive pollen that has been collected 
 by the second pair. Nearly all of this pollen is collected by the 
 pollen combs of the hind legs, and is transferred from the combs to 
 the pollen baskets or corbicula? in a manner to be described later. 
 
 It will thus be seen that the manipulation of pollen is a succes- 
 sive process, and that most of the pollen at least passes backward 
 from the point where it happens to touch the bee until it finally 
 reaches the corbicula? or is accidentally dislodged and falls from the 
 rapidly moving limbs. 
 
 ACTION OF THE FORELEGS AND MOUTHPARTS. 
 
 Although the pollen of some plants appears to be somewhat sticky, 
 it ma}' be stated that as a general rule pollen can not be successfully 
 manipulated and packed in the baskets without the addition of some 
 fluid substance, preferably a fluid which will cause the grains to 
 cohere. This fluid, the nature of which will be considered later, 
 comes from the mouth of the bee, and is added to the pollen which 
 is collected by the mouthparts and to that which is brought into con- 
 tact with the protruding tongue and maxilla?, and, as will appear, 
 this fluid also becomes more generally distributed upon the legs and 
 upon the ventral surface of the collecting bee. 
 
 "When a bee is collecting from the flowers of corn the mandibles are 
 actively engaged in seizing, biting, and scraping the anthers as the 
 bee crawls over the pendent stamens. Usually, but not always, the 
 tongue is protruded and wipes over the stamens, collecting pollen 
 and moistening the grains thus secured. Some of the pollen may 
 possibly be taken into the mouth. All of the pollen which comes in 
 contact with the mouthparts is thorough^ moistened, receiving more 
 fluid than is necessary for rendering the grains cohesive. This 
 exceedingly wet pollen is removed from the mouthparts by the fore- 
 legs (fig. 5) j and probably the middle legs also secure a little of it 
 directly, since they sometimes brush over the lower surface of the 
 face and the mouth. In addition to removing the very moist pollen 
 from the mouth the forelegs also execute cleansing movements over 
 the sides of the head and neck and the anterior region of the thorax, 
 thereby collecting upon their brushes a considerable amount of pollen 
 which has fallen directly upon these regions, and this is added to the 
 pollen moistened from the mouth, thereby becoming moist by contact. 
 The brushes of the forelegs also come in contact with the anterior 
 breast region, and the hairs which cover this area become moist with 
 the sticky exudation which the forelegs have acquired in the process 
 of wiping pollen from the tongue, maxillae, and mandibles. 
 
14 
 
 BEHAVIOR OF HONEY BEE IN POLLEN COLLECTING. 
 
 ACTION" OF THE MIDDLE LEGS. 
 
 The middle legs are used to collect the pollen gathered by the 
 forelegs and mouthparts, to remove free pollen from the thoracic 
 region, and to transport their load of pollen to the hind legs, placing 
 most of it upon the pollen combs of these legs, although a slight 
 amount is directly added to the pollen masses in the corbiculse. Most 
 of the pollen of the middle legs is gathered upon the conspicuous 
 brushes of the first tarsal segments or plantae of these legs. 
 
 In taking pollen from a foreleg the middle leg of the same side is ex- 
 tended in a forward direction and is either grasped by the flexed fore- 
 leg or rubbed over the foreleg as it is bent downward and backward. 
 In the former movement the foreleg flexes sharply upon itself until 
 
 Pig. 5. — A flying bee, showing the manner in which the forelegs and middle legs manipu- 
 late pollen. The forelegs are removing wet pollen from the mouthparts and face. The 
 middle leg of the right side is transferring the pollen upon its brush to the pollen 
 combs of the left hind planta. A small amount of pollen has already been placed in 
 the baskets. (Original.) 
 
 the tarsal brush and coxa nearly meet. The collecting brush of the 
 middle leg is now thrust in between the tarsus and coxa of the fore- 
 leg and wipes off some of the pollen from the foreleg brush. The, 
 middle leg brush is then raised and combs down over the flexed fore- 
 leg, thus removing additional pollen from the outer surface of this 
 leg. The middle leg also at times reaches far forward, stroking down 
 over the foreleg before it is entirely flexed and apparently combing 
 over with its tarsal brush the face and mouthparts themselves. 
 When the middle leg reaches forward to execute any of the above 
 movements the direction of the stroke is outward, forward, and then 
 back toward the body, the action ending with the brush of the leg in 
 contact with the long hairs of the breast and with those which spring 
 
ACTION OF MIDDLE LEGS. 
 
 15 
 
 from the proximal segments of the forelegs (coxa, trochanter, 
 femur). As a result of the oft-repeatecl contact of the brushes of 
 the middle and forelegs with the breast, the long, branched hairs 
 which cover this region become quite moist and sticky, since the 
 brushes of these two pair of legs are wet and the pollen which they 
 bear possesses a superabundance of the moistening fluid. Any dry 
 pollen which passes over this region and touches these hairs receives 
 moisture by contact with them. This is particularly true of the free 
 dry pollen which the middle pair of legs collect by combing over the 
 sides of the thorax. 
 
 The pollen upon the middle legs is transferred to the hind legs in 
 at least two ways. By far the larger amount is deposited upon the 
 pollen combs which lie on the inner surfaces of the plantse of the 
 
 Fig. G. — A bee upon the wing, showing the position of the middle legs when they touch 
 and pat down the pollen masses. A very slight amount of pollen reaches the corbiculas 
 through this movement. (Original.) 
 
 hind legs. To accomplish this a middle leg is placed between the 
 plantse of the two hind legs, which are brought together so as to grasp 
 the brush of the middle leg, pressing it closely between them, but 
 allowing it to be drawn toward the body between the pollen combs 
 of the two hind legs. (See fig. 5.) This action results in the trans- 
 ference of the pollen from the middle-leg brush to the pollen combs 
 of the hind leg of the opposite side, since the combs of that leg scrape 
 over the pollen-laden brush of the middle leg. This action may take 
 place while the bee is on the wing or before it leaves the flower. 
 
 The middle legs place a relatively small amount of pollen directly 
 upon the pollen masses in the corbiculae. This is accomplished when 
 the brushes of the middle legs are used to pat down the pollen ma»v-s 
 and to render them more compact. (See fig. G.) The legs are used 
 
16 BEHAVIOK oi' HONEY BSE IX POLLEN COLLECTING. 
 
 for this purpose quite often during the process of Loading the baskets, 
 
 and a small amount of pollen is incidentally added to the n, 
 when the brushes come into contact with them. A misinterpretation 
 of this action has led some observers into the erroneous belief that 
 all or nearly all of the corbicular pollen is scraped from the middle- 
 leg brushes by the hairs which fringe the sides of the baskets. The 
 middle legs do not scrape across the baskets, but merely pat down- 
 ward upon the pollen which is there accumulating. 
 
 It is also possible that, in transferring pollen from the middle leg 
 of one side to the planta of the opposite hind leg, the middle-leg 
 brush may touch and rub over the pecten of the hind leg and thus 
 directly place some of its pollen behind the pecten spines. Such a 
 result is, however, very doubtful. 
 
 ACTION OF THE HIND LEGS. 
 
 The middle legs contribute the major portion of the pollen which 
 reaches the hind legs, and all of it in cases where all of the pollen 
 first reaches the bee in the region of the mouth. However, when 
 much pollen falls upon the body of the bee the hind legs collect a 
 little of it directly, for it falls upon their brushes and is collected 
 upon them when these legs execute cleansing movements to remove 
 it from the ventral surface and sides of the abdomen. All of the 
 pollen which reaches the corbiculse, with the exception of the small 
 amount placed there by the middle legs when they pat down the 
 pollen masses, passes first to the pollen combs of the plantae. 
 
 When in the act of loading pollen from the plantar brushes to the 
 corbicula? the two hind legs hang beneath the abdomen with the tibio- 
 femoral joints well drawn up toward the body. (See fig. 7.) The 
 two plantae lie close together with their inner surfaces nearly parallel 
 to each other, but not quite, since they diverge slightly at their distal 
 ends. The pollen combs of one leg are in contact with the pecten 
 comb of the opposite leg. If pollen is to be transferred from the 
 right planta to the left basket, the right planta is drawn upward in 
 such a manner that the pollen combs of the right leg scrape over 
 the pecten spines of the left. By this action some of the pollen is 
 removed from the right plantar combs and is caught upon the outer 
 surfaces of the pecten spines of the left leg. 
 
 This pollen now lies against the pecten and upon the flattened 
 distal end of the left tibia. At this moment the planta of the left 
 leg is flexed slightly, thus elevating the auricle and bringing the auri- 
 cular surface into contact with the pollen which the pecten has just 
 received. By this action the pollen is squeezed between the end of the 
 tibia and the surface of the auricle and is forced upward against the 
 distal end of the tibia and on outward into contact with the pollen 
 mass accumulating in the corbicula. As this act, by which the left 
 
ACTION OF HIND LEGS. 
 
 17 
 
 basket receives a small contribution of pollen, is being completed, the 
 right leg is lowered and the pecten of this leg is brought into contact 
 with the pollen combs of the left planta, over which they scrape as 
 the left leg is raised, thus depositing pollen upon the lateral surfaces 
 of the pecten spines of the right leg. (See fig. 7.) 
 
 Right and left baskets thus receive alternately successive contribu- 
 tions of pollen from the planta of the opposite leg. These loading 
 movements are executed with great rapidity, the legs rising and fall- 
 ing with a pump-like motion. A very small amount of pollen is 
 loaded at each stroke and many strokes are required to load the 
 baskets completely. 
 
 If one attempts to obtain, from the literature of apiculture and 
 zoology, a knowledge of the method by which the pollen baskets 
 
 Fig. 7. — A bee upon the wing, showing the manner in which the hind legs are held during 
 the basket-loading- process. Pollen is being scraped by the pecten spines of tbe right 
 leg from the pollen combs of the left hind planta. (Original.) 
 
 themselves are loaded, he is immediately confused by the diversity of 
 the .accounts available. The average textbook of zoology follows 
 closely Cheshire's (188G) description in which he says that "the legs 
 are crossed, and the metatarsus naturally scrapes its comb face on the 
 upper edge of the opposite tibia in the direction from the base of the 
 combs toward their tips. These upper hairs * * * are nearly 
 straight, and pass between the comb teeth. The pollen, as removed, 
 is caught by the bent-over hairs, and secured. Each scrape adds to 
 the mass, until the face of the joint is more than covered, and the 
 hairs just embrace the pellet." Franz (190G) states that (translated) 
 " the final loading of the baskets is accomplished by the crossing over 
 of the hind-tarsal segments, which rub and press upon each other." 
 Many other observers and textbook writers evidently believed that 
 the hind legs were crossed in the loading process. 
 61790°— Bull. 121—12 3 
 
18 BEHAVIOR OF HONEY BEE IN POLLEN COLLECTING. 
 
 On the other hand, it is believed by some that the middle legs are 
 directly instrumental in filling the baskets. This method is indicated 
 in the following quotation from Fleischmann and Zander (1910) 
 (translated) : 
 
 The second pair of legs transfer the pollen to the hind legs, where it is 
 heaped up in the pollen masses. The tibia of each hind leg is depressed on its 
 outer side, and upon the edges of this depression stand two rows of stiff hairs 
 which are bent over the groove. The brushes of the middle pair of legs rub 
 over these hairs, liberating the pollen, which drops into the baskets. 
 
 A suggestion of the true method is given by Hommell (190G), 
 though his statements are somewhat indefinite. After describing 
 the method by which pollen is collected, moistened, and passed to 
 the middle legs he states that (translated) "the middle legs place 
 their loads upon the pollen combs of the hind legs. There the sticky 
 pollen is kneaded and is pushed across the pincher (a traverse la 
 pince), is broken up into little masses and accumulates within the 
 corbicula. In accomplishing this, the legs cross and it is the tarsus 
 of the right leg which pushes the pollen across the pincher of the 
 left, and reciprocally. The middle legs never function directly in 
 loading the baskets, though from time to time their sensitive ex- 
 tremities touch the accumulated mass, for the sake of giving assur- 
 ance of its position and size." 
 
 The recent valuable papers of Sladen (1911, 1912, «, &, c, d, and <?), 
 who was the first to present a true explanation of the function of 
 the abdominal scent gland of the bee, give accounts of the process 
 by which the pollen baskets are charged, which are in close accord 
 with the writer's ideas on this subject. It is a pleasure to be able to 
 confirm most of Sladen's observations and conclusions, and weight is 
 added to the probable correctness of the two descriptions and in- 
 terpretations of this process by the fact that the writer's studies and 
 the conclusion based upon them were made prior to the appearance 
 of Sladen's papers and quite independent of them. His description 
 of the basket-loading process itself is so similar to the writer's own 
 that a complete quotation from him is unnecessary. A few differences 
 of opinion will, however, be noted w T hile discussing some of the move- 
 ments which the process involves. As will later be noted, our ideas 
 regarding the question of pollen moistening, collecting, and transfer- 
 ence are somewhat different. 
 
 ADDITIONAL DETAILS OF THE BASKET-LOADING PROCESS. 
 
 The point at w T hich pollen enters the basket can best be determined 
 by examining the corbiculse of a bee shortly after it has reached a 
 flower and before much pollen has been collected. Within each 
 pollen basket of such a bee is found a small mass of pollen, which lies 
 
ADDITIONAL DETAILS OF BASKET-LOADING PROCESS. 
 
 19 
 
 along the lower or distal margin of the basket. (See fig 8, a.) It is 
 in this position because it has been scraped from the planta of the 
 opposite leg b} T the pecten comb and has been pushed upward past 
 the entrance of the basket by the continued addition of more from 
 below, propelled by the successive strokes of the auricle. Closer 
 
 Fig. 8. — Camera drawings of the left hind legs of worker bees to show the manner in 
 which pollen enters the basket, a, Shows a leg taken from a bee which is just begin- 
 ning to collect. It had crawled over a few flowers and had flown in the air about five 
 seconds at the time of capture. The pollen mass lies at the entrance of the basket, 
 covering over the fine hairs which lie along this margin and the seven or eight short 
 stiff spines which spring from the floor of the corbicula immediately above its lower 
 edge. As yet the pollen has not come in contact with the one long hair which rises 
 from the floor and arches over tbe entrance. The planta is extended, thus lowering 
 the auricle ; b, represents a slightly later stage, showing the increase of pollen. The 
 planta is flexed, raising the auricle. The hairs which extend outward and upward from 
 the lateral edge of the auricle press upon the lower and outer surface of the small 
 pollen mass, retaining it and guiding it upward into the basket ; c, d, represent sligbtly 
 later stages in the successive processes by which additional pollen enters the basket. 
 (Original.) 
 
 examination of the region between the pecten and the floor of the 
 basket itself shows more pollen, which is on its way to join that 
 already squeezed into the basket. 
 
 If the collecting bee is watched for a few moments the increase will 
 readily be noted and the fact will be established that the accumulat- 
 ing mass is gradually working upward or proximally from the lower 
 
20 BEHAVIOR OF HONEY BEE IN POLLEN COLLECTING. 
 
 or distal edge of the corbicula and is slowly covering the floor of this 
 receptacle. (See fig*. 8, &, c, and d.) In many instances the suc- 
 cessive contributions remain for a time fairly separate, the whole 
 mass being marked by furrows transverse to the long axis of the tibia. 
 
 Sladen (1912. b) notes the interesting fact that in those rather 
 exceptional cases when a bee gathers pollen from more than one 
 species of flowers the resulting mass within the corbicula will show 
 a stratification parallel to the distal end, a condition which could 
 result only from the method of loading here indicated. 
 
 As the pollen within the basket increases in amount it bulges out- 
 ward, and projects downward below the lower edge of the basket. 
 It is held in position by the long hairs which fringe the lateral sides 
 of the basket, and its shape is largely determined by the form of 
 these hairs and the direction in which they extend. When the basket 
 is fully loaded the mass of pollen extends laterally on both sides of 
 the tibia, but projects much farther on the posterior side, for on this 
 side the bounding row of hairs extends outward, while on the anterior 
 edge the hairs are more curved, folding upward and over the basket. 
 As the mass increases in thickness by additions from below it is held 
 in position by these long hairs which edge the basket. They are 
 pushed outward and many of them become partly embedded in the 
 pollen as it is pushed up from below. When the pollen grains are 
 small and the whole mass is well moistened the marks made by some 
 of the hairs will be seen on the sides of the load. (See fig. 9, a.) 
 These scratches are also transverse in direction and they show that 
 the mass has been increased by additions of pollen pushed up from 
 below. 
 
 Even a superficial examination of a heavily laden basket shows 
 the fallacy of the supposition that the long lateral fringing hairs are 
 used to comb out the pollen from the brushes of either the hind or 
 middle legs by the crossing of these legs over the lateral edges of the 
 baskets. They are far from sufficiently stiff to serve this purpose, 
 and their position with relation to the completed load shows con- 
 clusively that they could not be used in the final stages of the loading 
 process, for the pollen mass has completely covered many of them 
 and its outer surface extends far beyond their ends. The} 7 serve 
 merely to hold the pollen in place and to allow the load to project 
 beyond the margins of the tibia. 
 
 The auricle plays a very essential part in the process of loading 
 the basket. This structure comprises the whole of the flattened 
 proximal surface of the planta, except the joint of articulation itself, 
 and it extends outward in a posterior direction a little beyond the 
 remaining plantar edge. The surface of the auricle is covered over 
 with many blunt, short spines and its lateral margin is bounded by 
 a row of short rather pliable hairs, branched at their ends. When 
 
ADDITIONAL DETAILS OF BASKET-LOADING PROCESS. 21 
 
 the planta is flexed the auricle is raised and its surface approaches 
 the distal end of the tibia, its inner edge slipping up along the pecten 
 spines and its outer hairy edge projecting into the opening which 
 leads to the pollen basket. (See fig. 8, b.) With each upward stroke 
 of the auricle small masses of pollen which have been scraped from the 
 plantar combs by the pecten are caught and compressed between the 
 spiny surface of the auricle and the surface of the tibia above it. 
 The pressure thus exerted forces the pasty pollen outward and up- 
 ward, since it can not escape past the base of the pecten, and directs 
 it into the entrance to the corbicula. The outward and upward slant 
 of the auricular surface and the projecting hairs with which the outer 
 edge of the auricle is supplied also aid in directing the pollen toward 
 the basket. Sladen (1911) states that in this movement the weak 
 wing of the auricle is forced backward, and thus allows the escape of 
 pollen toward the basket entrance, but this appears both doubtful and 
 unnecessary, since the angle of inclination of the auricular surface 
 gives the pollen a natural outlet in the proper direction. 
 
 If the corbicula already contains a considerable amount of pollen 
 the contributions which are added to it at each stroke of the auricle 
 come in contact with that already deposited and form a part of this 
 mass, which increases in amount by continued additions from below. 
 If, however, the corbicula is empty and the process of loading is just 
 beginning, the first small bits of pollen which enter the basket must 
 be retained upon the floor of the chamber until a sufficient amount 
 has accumulated to allow the long overcurving hairs to offer it effec- 
 tive support. The sticky consistency of the pollen renders it likely 
 to retain contact with the basket, and certain structures near the 
 entrance give additional support. Several small sharp spines, seven 
 or eight in number, spring from the floor of the basket immediately 
 within the entrance, and the entire lower edge of the corbicula is 
 fringed with very small hairs which are branched at their ends. 
 (See fig. 3.) One large hair also springs from the floor of the basket, 
 somewhat back from the entrance, which may aid in holding the 
 pollen, but it can not function in this manner until a considerable 
 amount has been collected. 
 
 As the pollen mass increases in size and hangs downward and back- 
 ward over the pecten and auricle it shows upon its inner and lower 
 surface a deep groove which runs outward from the entrance to the 
 basket. (See fig. 9, b.) This groove results from the continued im- 
 pact of the outer end of the auricle upon the pollen mass. At each 
 upward stroke of the auricle its outer point comes in contact with 
 the stored pollen as soon as the mass begins to bulge backward from 
 the basket. 
 
 Although the process is a rather delicate one, it is entirely pos- 
 sible so to manipulate the hind legs of a recently killed bee that the 
 
22 
 
 BEHAVIOR OF HONEY BEE IX POLLEN COLLECTING. 
 
 -^ct 
 
 corbiculae of the two legs receive loads of pollen in a manner similar 
 to that above described. To accomplish this successful!}* the operator 
 must keep the combs of the planta? well supplied with moistened 
 pollen. If the foot of first one leg and then the other is grasped 
 with forceps and so guided that the pollen combs of one leg rasp over 
 the pecten spines of the other, the pollen from the combs will be 
 transferred to the corbicula?. To continue the loading process in a 
 
 proper manner, it is also nec- 
 essary to flex the planta of 
 each leg just after the pollen 
 combs of the opposite leg 
 have deposited pollen behind 
 the pecten. By this action 
 the auricle is raised, com- 
 pressing the pollen which 
 the pecten has secured, and 
 forcing some upward into 
 the corbicula. Bees' legs 
 which have been loaded in 
 this artificial manner show 
 pollen masses in their cor- 
 bicula^ which are entirely 
 similar in appearance to 
 those formed by the labors 
 of the living bee. More- 
 over, by the above method 
 of manipulation the pollen 
 appears first at the bottom 
 of the basket, along its lower 
 margin, gradually extends 
 upward along the floor of 
 the chamber, comes in con- 
 tact with the overhanging 
 hairs, and is shaped by them 
 in a natural manner. All 
 attempts to load the baskets 
 by other movements, such as 
 crossing the hind legs and 
 scraping the plantar combs over the lateral edges of the baskets, 
 give results which are entirely different from those achieved by the 
 
 Fig. 0. — Inner surface of the right hind leg of a 
 worker bee which bears a- complete load of 
 pollen, a, Scratches in the pollen mass caused 
 by the pressure of the long projecting hairs 
 of the basket upon the pollen mass as it has 
 been pushed up from below ; b, groove in the 
 pollen mass made bj T the strokes of the auricle 
 :is the mass projects outward and backward 
 from the basket. (Original.) 
 
 living bee. 
 
 POLLEN MOISTENING. 
 
 Many descriptions have been written by others of the method by 
 which pollen is gathered and moistened. Some of these are indefi- 
 nite, some are incorrect, while others are. in part, at least, similar 
 
POLLEN MOISTENING. 23 
 
 to my own interpretation of this process. A few citations will here 
 be given : 
 
 The bee first strokes the head and the proboscis with the brushes of the 
 forelegs and moistens these brushes with a little honey from the proboscis, so 
 that with later strokes all of the pollen from the head is collected upon these 
 brushes. Then the middle-leg brushes remove this honey-moistened pollen from 
 the forelegs and they also collect pollen from the breast and the sides of the 
 thorax. — [Translation from Alefeld, 1861.] 
 
 In his account of the basket-loading process Alefeld assigns to 
 the middle-leg brushes the function of assembling all of the pollen, 
 even that from the plantar combs, and of placing it on the corbicula?, 
 this latter act being accomplished by combing over the hairy edge of 
 each basket with the middle-leg brush of the same side. 
 
 It appears probable that the bee removes the pollen from the head, breast, 
 and abdomen by means of the hairy brushes which are located upon the medial 
 sides of the tarsal segments of all of the legs, being most pronounced upon the 
 hind legs. The pollen is thus brought together and is carried forward to the 
 mouth, where it is moistened with saliva and a little honey. — [Translation from 
 Franz, 1906.] 
 
 Franz then says that this moistened pollen is passed backward and 
 loaded. 
 
 Since the pollen of many plants is sticky and moist it adheres to the surface 
 of the basket. Dry pollen is moistened by saliva, so that it also sticks, — 
 [Translation from Fleischmann and Zander. 1910.] 
 
 Pollen is taken from flowers principally by means of the tongue, but at times, 
 also, by the mandibles, by the forelegs, and middle legs. The brushes of the 
 hind legs also load themselves, collecting from the hairs of the body. The pollen 
 dust thus gathered is always transmitted to the mouth, where it is mixed with 
 saliva. — [Translation from Hommell, 1906.] 
 
 Sladen considers the question of how pollen is moistened by the 
 honey bee. bumblebee ( bumblebee) , and some other bees, but does not 
 appear to reach definite conclusions. In one of his papers (1912. c) 
 he states that the pollen of some plants may be found in the mouth 
 cavity and in the region of the mouth, but he reaches the conclusion 
 that this pollen is comparatively " dry,'' using the word in a " rela- 
 tive sense." He asserts that " nowhere but on the corbicula and 
 hind metatarsal brushes did I find the sticky pollen, except some- 
 times on the tips of the long, branched hairs on the back (upper) 
 edges of the tibiae and femora of the middle legs, and then only 
 in heavily laden bees, where it is reasonable to suppose it had 
 collected accidentally as the result of contact with the hind metatarsal 
 brushes." 
 
 These and other considerations lead Sladen to think that, in the 
 case of the bumblebee at least, the pollen " may be moistened on the 
 hind metatarsus with the tongue." He states that the tongue of 
 the bumblebee is of sufficient leno'th to reach the hind metatarsus 
 
24 BEHAVIOR OF HONEY BEI. TX POLLEN COLLECTING. 
 
 (planta) and that it might rub over the brushes of the metatarsi 
 or be caught between them when they are approximated and thus 
 moisten the two brushes simultaneously. However, he has never 
 seen the tongue of the collecting honey bee brought near to the hind 
 legs, and it appears probable to him that it can not easily reach them. 
 " Possibly the middle or front legs are used as agents for conveying 
 the honey" (in the case of the honey bee). "In the humblebee the 
 tongue is longer, and it could more easily moisten the hind legs in 
 the way suggested." 
 
 In an earlier paper Sladen (1912, a) gives the following as his 
 opinion of the " way in which pollen dust is moistened with nectar," 
 although he states that this is one of the points " which still remains 
 obscure " : 
 
 The only satisfactory manner in which, it seems to me, this can be done is 
 for the tongue to lick the tarsi or metatarsi of the forelegs, which are covered 
 with stiff bristles, well suited for holding the nectar, the nectar being then 
 transferred to the metatarsal brushes on the middle legs, and from these, again, 
 to the metatarsal brushes on the hind legs. The latter being thus rendered 
 sticky, the pollen dust would cling to them. The different pairs of legs were 
 certainly brought together occasionally, but not after every scrape of the 
 hind metatarsi, and their movements were so quick that it was impossible 
 to see what was done. Still, several pollen-collecting bees that I killed had the 
 tarsi and metatarsi of the forelegs and the metatarsal brushes of the middle 
 and hind legs moistened with nectar, and I think it probable that the moisten- 
 ing process, as outlined, is performed, as a rule, during the flight from flower 
 to flower. 
 
 Sladen (1912, c) also considers the possibility that the fluid which 
 moistens the pollen might be secreted through the comb at the end 
 of the tibia, through the tibio-tarsal joint, or from the surface of the 
 auricle, but finds no evidence of glandular openings in these regions. 
 A suggestion of a similar nature, apparently unknown to Sladen, 
 was made by T\ T olff (1873), who describes "sweat-glands" which, 
 he claims, are located within the hind tibia and the planta, and 
 w r hich pour a secretion upon the surface of the corbicula and upon 
 the upper end of the planta through many minute openings located 
 at the bases of hairs, particularly those which arise from the lateral 
 margins of the corbicula. Wolff is convinced that the fluid thus 
 secreted is the essential cohesive material by which the grains of 
 pollen are bound together to form the solid mass which fills each 
 fully loaded basket. He noticed that the mouthparts are used to 
 collect pollen, and that some of it is moistened with " honey " or 
 " nectar," but he does not consider that the fluid thus supplied is 
 sufficient to explain adequately the facility with which the collecting 
 bee brings together the scattered grains of pollen and packs them 
 away securely in the baskets. Wolff's description of the basket-load- 
 ing process itself is strikingly similar to that advocated later b}' 
 Cheshire. 
 
POLLEN MOISTENING. 25 
 
 The writer is not prepared to deny the possibility that the surface 
 of the chitin of the hind legs of worker bees may be moistened by 
 the secretion of glands which lie beneath it, but he is convinced that 
 any fluid thus secreted bears little or no relation to the cohesion of 
 the pollen grains within the baskets. Sections and dissected prepa- 
 rations of the hind legs of worker bees show certain large cells which 
 lie within the cavity of the leg and which may function as secreting 
 gland cells; but similar structures occur in even greater numbers 
 within the hind legs of the drone and they are found within the hind 
 legs of the queen. 
 
 As has been noted, the extreme moisture of the plantar combs and 
 of the tibio-tarsal articulation of the hind leg is readily understood 
 when one recalls the manner in which moist pollen is compressed 
 between the auricle and the tibial surface above it. 
 
 From the account already given it is evident that, in the opinion 
 of the writer, the mouth is the source from which the pollen-moisten- 
 ing fluid is obtained. It is extremely difficult to determine with 
 absolute accuracy the essential steps involved in the process of adding 
 moisture to the pollen. In an endeavor to solve this problem the 
 observer must of necessity consider a number of factors, among which 
 may be noted (1) the location upon the body of the collecting bee 
 of " moist " and of comparatively " dry " pollen, (2) the movements 
 concerned in the pollen-gathering and pollen-transferring processes, 
 (3) the relative moisture of those parts which handle pollen, (4) the 
 chemical differences between the natural pollen of the flower and 
 that of the corbiculse and of the cells of the hive, and (5) the observer 
 must endeavor to distinguish between essential phenomena and those 
 which are merely incidental or accidental. 
 
 In the first place it should be noted that the relative dampness of 
 pollen within the corbiculse depends very largely upon the character 
 of the flower from which the pollen grains are gathered. When 
 little pollen is obtained it is much more thoroughly moistened, and 
 this is particularly true in cases when the pollen is all, or nearly all, 
 collected in the region of the mouth, the forelegs, and head. When 
 a bee takes pollen from white or sweet clover practically all of it 
 first touches the bee in these regions. It immediately becomes moist, 
 and in this condition is passed backward until it rests within the 
 baskets. There is here no question of "dry" and "wet" pollen, 
 or of collecting movements to secure dry pollen from other regions 
 of the body, or of the ultimate method by which such free, dry pol- 
 len becomes moist. 
 
 The sticky fluid which causes pollen grains to cohere is found upon 
 all of the legs, in the region of their brushes, although the pollen 
 combs and auricles of the hind legs are likely to show it in greatest 
 abundance, since nearly all of the pollen within each basket has 
 
26 BEHAVIOR OF HONEY BEE IN POLLEN COLLECTING. 
 
 passed over the auricle, has been pressed upward and squeezed be- 
 t ween the auricle and the end of the tibia and the pollen mass above, 
 and by this compression has lost some of its fluid, which runs down 
 over the auricle and onto the combs of the planta. It is not necessary 
 to invoke any special method by which these areas receive their 
 moisture. The compressing action of the auricle squeezing heavily 
 moistened pollen upward into the basket is entirely sufficient to 
 account for the abundance of sticky fluid found in the neighborhood 
 of each hind tibio-tarsal joint. As has been noted, the brushes of 
 the forelegs acquire moisture directly by stroking over the proboscis 
 and by handling extremely moist pollen taken from the mouthparts. 
 The middle-leg brushes become moist by contact with the foreleg and 
 hind-leg brushes, probably also by touching the mouthparts them- 
 selves, and by passing moist pollen backward. The hairy surface of 
 the breast is moistened by contact with the fore and mid leg brushes 
 and with the moist pollen which they bear. 
 
 The problem of the method of pollen moistening is somewhat more 
 complicated in the case of flowers which furnish an excessive supply. 
 ruder such conditions the entire ventral surface of the collecting bee 
 becomes liberally sprinkled with pollen grains which either will be 
 removed and dropped or will be combed from the bristles and branch- 
 ing hairs, kneaded into masses, transferred, and loaded. The ques- 
 tion naturally arises whether the movements here are the same as 
 when the plant yields but a small amount of pollen which is collected 
 by the mouthparts and anterior legs. In the opinion of the writer 
 they are essentially the same, except for the addition of cleansing 
 movements, executed chiefly by the middle and hind legs for the col- 
 lection of pollen which has fallen upon the thorax, upon the abdomen, 
 and upon the legs themselves. Indeed it is questionable as to just 
 how much of this plentiful supply of free pollen is really used in 
 forming the corbicular masses. "Without doubt much of it falls from 
 the bee and is lost, and in cases where it is extremely abundant and 
 the grains are very small in size an appreciable amount still remains 
 entangled among the body-hairs when the bee returns to the hive. 
 Yet it is also evident that some of the dry pollen is mingled with the 
 moistened material which the mouthparts and forelegs acquire and 
 together with this is transferred to the baskets. 
 
 In all casas the pollen-gathering process starts with moist pollen 
 from the mouth region. This pollen is passed backward, and in its 
 passage it imparts additional moisture to those body regions which 
 it touches, the brushes of the fore and middle legs, the planta? of the 
 hind legs, and the hairs of the breast which are scraped over by the 
 fore and middle leg brushes. This moist pollen, in its passage back- 
 ward, may also pick up and add to itself grains of dr}' pollen with 
 w T hich it accidentally comes in contact. Some of the free, dry pollen 
 
POLLEN MOISTENING. 27 
 
 which falls upon the moist brushes or upon the wet hairs of the 
 thorax is also dampened. Some of the dry pollen which is cleaned 
 from the body by the action of all of the legs meets with the wet- 
 brushes or with the little masses of wet pollen and itself becomes wet 
 by contact. Pollen grains which reach the corbiculse either dry or 
 but slightly moistened are soon rendered moist by contact with those 
 already deposited. Little pollen gets by the sticky surfaces of the 
 combs of the plantar or past the auricles without becoming thoroughly 
 moist. 
 
 Sladen (1912, c) very aptly compares the mixture of dry pollen 
 with wet to the kneading of wet dough with dry flour and suggests 
 that the addition of dry pollen may be of considerable advantage, 
 since otherwise the brushes, particularly those of the hind legs, 
 would become sticky, " just as the board and rolling pin get sticky 
 in working up a ball of dough if one does not add flour. 1 ' The addi- 
 tion of a considerable amount of dry pollen gives exactly this result, 
 for the corbiculse then rapidly become loaded with pollen mixed 
 with a minimum supply of moisture and the brushes remain much 
 dryer than would otherwise be the case. However, if too much dry 
 pollen is added the resulting loads which the bees carry back to the 
 hives are likely to be irregular, for the projecting edges of the masses 
 may crumble through lack of a sufficient amount of the cohesive 
 material by which the grains are bound together. 
 
 On the other hand, it does not appear at all necessary to mix much 
 dry pollen with the wet, nor do the brushes become sufficiently 
 " sticky " from the presence of an abundance of the moistening fluid 
 to endanger their normal functional activity. I have observed bees 
 bringing in pollen masses which were fairly liquid with moisture, 
 and the pollen combs also were covered with fluid, yet the baskets 
 were fully and symmetrically loaded. 
 
 Sladen's different interpretations of the pollen-moistening process 
 are rather confusing, and it is difficult to distinguish between what 
 he states as observed facts and what he puts forward as likely 
 hypotheses. He agrees with me in his observation that all of the 
 legs become moist in the region of their brushes and also in his sup- 
 position that this moisture is transferred to them from the mouth. 
 In this moistening process my observations show that the fluid con- 
 cerned is passed backward by the contact, of the middle-leg brushes 
 with the wet foreleg brushes and that the middle-leg brushes in turn 
 convey moisture to the plantse as they rub upon them. I am also 
 convinced that the wet pollen grains furnish additional moisture to 
 the brushes as they pass backward, and this is particularly true in 
 the case of the extremely moist surfaces of the auricles and the pollen 
 combs of the planta, since here moisture is pressed from the pollen 
 upon these areas. The pollen upon the fore and middle leg brushes 
 is not always " dry ; ' even in " a relative sense." 
 
28 
 
 BEHAVIOR OF HONEY BEE IX POLLEN COLLECTING. 
 
 In describing pollen manipulation several writers state that dry 
 pollen is picked up by the brushes of the legs and is carried forward 
 to the mouth, there moistened (according to some, masticated), and 
 is then carried backward by the middle legs for loading. Obviously 
 such accounts do not apply to cases in which all of the pollen is col- 
 lected by mouthparts and forelegs. Do they apply in case> where 
 much pollen falls on the body and limbs? Without doubt a certain 
 amount of this free pollen is brought forward when the middle legs, 
 bearing some of it, sweep forward and downward over the forelegs, 
 mouthparts, and breast. However, it does not appear to the writer 
 that this dry pollen is carried to the mouth for the specific purpose of 
 moistening it, or that it is essential to its moistening that it be 
 brought in contact Avith the mouth. Some of it touches the moist 
 hairs on the forelegs and breast and is moistened by contact. All 
 that remains on the brushes of the middle legs secures moisture from 
 these brushes or from wet pollen which the brushes collect from the 
 mouthparts or forelegs. The supposed necessity of carrying forward 
 pollen to the mouth for moistening is a delusion. Some is acci- 
 dentally brought forward and into contact with the mouth and gets 
 wet, but the process is not essential. 
 
 If the pollen which bees transport to their hives has been moistened 
 w T ith some fluid substance which causes the grains to cohere, this 
 addition should be indicated by differences in the results of an analy- 
 sis of pollen from a plant as compared with that found in the cor- 
 bieulse of a bee which has been working on this plant. For the sake 
 of determining this difference and in an endeavor to ascertain, if 
 possible, the. approximate nature of the added fluid, analyses were 
 made of three kinds of pollen, as follows: (1) Pollen collected by 
 hand from the corn plant itself; (2) pollen taken from the corbiculse 
 of bees which had secured their supply from corn; (3) pollen stored 
 in the cells of the hive. In the first two cases pollen from the same 
 species of plant (corn) was used. The material from the cells of the 
 hive was composed largely of corn pollen, but contained an admixture 
 of some other pollens. 
 
 The writer is indebted to Dr. P. B. Dunbar, of the Bureau of 
 Chemistry, for the following analyses : 
 
 » 
 
 Pollen 
 
 direct 
 from 
 corn. 
 
 Corn pol- 
 len from 
 corbicula. 
 
 Stored 
 pollen 
 from 
 hive. 
 
 Total solids 
 
 53.47 
 
 4G.53 
 2.87 
 
 '_». 77 
 5.79 
 
 66.94 
 
 33.06 
 
 11.07 
 
 3.06 
 
 14.29 
 
 79.66 
 
 
 20.34 
 
 
 17.90 
 
 
 2.25 
 
 Total reducing sngai 
 
 20. 27 
 
 Dry basis: 
 
 Reducing sugar 
 
 L37 
 5.18 
 
 16.54 
 4.57 
 
 22. 47 
 
 2.82 
 
 
 
 
 10.55 
 
 ft 
 
 21.11 
 
 
 
 
STORING POLLEN IN THE HIVE. 29 
 
 These analyses show conclusively that a very large amount of 
 sugar has been added to the pollen by the time it reaches the cor- 
 biculae. Calculated on a dry basis just about twice as much sugar is 
 present in the basket pollen as in that from the corn plant. Xot only 
 is this so, but the additional fact is disclosed that over three times as 
 much reducing sugar is present in the corbicular pollen as sucrose. 
 This latter result indicates that honey (largely a reducing sugar) 
 rather than nectar (containing more sucrose) is the chief sugar in- 
 gredient of the corbicular pollen. The additional amount of sugar 
 (here again a reducing sugar) in the stored pollen of the hive is 
 what might be expected, since it is supposed that the workers add 
 honey and possibly other ingredients to the pollen within the 
 storage cells. 
 
 The total solid percentages, corn 53.47, corbicula 66.94, stored 
 pollen 79.66, also show that the fluid substance which is added is one 
 highly charged with solids, a condition which honey amply fulfills. 
 
 In the descriptions which have been cited of the pollen-gathering 
 process in which the mouth is supposed to supply the requisite fluid 
 three substances are mentioned: Nectar, honey, and saliva. The 
 analyses herein given indicate that reducing sugar is mingled with 
 the pollen, and in the case of corn it is indicated that honey is used 
 in greater abundance. Without doubt a certain amount of saliva 
 also finds its way to the pollen, but the proportion of this substance 
 has not been determined. This salivary fluid may have adhesive 
 qualities, but this is scarcely necessary, since honey alone is amply 
 sufficient for this purpose. 
 
 It appears probable that the fluid which a bee adds to the pollen 
 which it is collecting varies somewhat in amount, since the pollen of 
 different plants differs considerably in moisture content and that of 
 the same plant will differ in this respect at different times. Pollen 
 collected in the early morning before the dew has left the plant is 
 much more moist than that found upon the same plant later in the 
 day, and the grains, if taken when moist, have a natural tendency to 
 become aggregated and form small masses. Moreover, this may ex- 
 plain the fact that bees make their pollen-collecting trips during the 
 morning hours, rather than in the afternoon, although some may be 
 seen upon the flowers throughout the whole day. 
 
 STORING POLLEN IN" THE HIVE. 
 
 When the bee has fully loaded its baskets and before it returns to 
 the hive it often spends a little time upon the plant from which it 
 has been collecting, occupied with the task of cleaning scattered 
 grains of pollen from its body and of patting down securely the loads 
 which it has obtained. Upon its return to the hive it hurries within 
 and seeks for a suitable place in which to deposit the pollen. Some 
 
30 BEHAVIOR OP HONEY BEE IN POLLEN COLLECTING. 
 
 returning bees walk leisurely over the combs and loiter among their 
 sister workers, while others appear to be greatly agitated, shaking 
 their bodies and moving their Avings as though highly excited. 
 Many pollen-bearing bees appear eager to receive food upon their 
 return to the hive, and they will solicit it from other workers or 
 take it from the honey-storage cells. The workers of the hive at 
 times take a little of the fresh pollen from the baskets of the laden 
 bee, nibbling it off with their mandibles or rasping off grains with 
 their tongues. 
 
 If the combs of a colony are examined, stored pollen will be found 
 in various parts of the hive. In the brood frames the greatest amount 
 is located above and at the sides of the brood and between this and 
 the stored honey. Cells scattered through the brood from which 
 young bees have lately emerged may also contain pollen. In the 
 outer frames of the hive, where brood is less likely to be found, 
 nearly all of the cells may be packed with pollen, or honey-storage 
 cells may be found interspersed with those filled with pollen. As a 
 rule pollen is not stored in drone comb, although this occasionally 
 happens. 
 
 As the pollen-bearing bee crawls over the combs it appears to be 
 searching for a suitable cell in which to leave its load. It sticks 
 the head into cell after cell until finally one is located which meets 
 its requirements, although it is an open question as to why any one of 
 a group should be chosen rather than another. This selected cell 
 may already contain some pollen or it may be empty. If partly filled, 
 the pollen which it contains is likely to be from the same species of 
 plant as that which the bee carries, although different kinds of pollen 
 are often stored in the same cell. 
 
 In preparation for the act of unloading the bee grasps one edge 
 of the cell with its forelegs and arches its abdomen so that the pos- 
 terior end of the abdomen rests upon the opposite side of the cell. The 
 body is thus held firmly and is braced by these two supports with the 
 head and anterior thoracic region projecting over one of the neigh- 
 boring cells. The hind legs are thrust down into the cell and hang 
 freely within it, the pollen masses being held on a level with the outer 
 edge of the cell, or slightly above it. The middle leg of each side 
 is raised and its planta is brought into contact with the upper 
 (proximal) end of the tibia of the same side and with the pollen mass. 
 The middle leg now presses downward upon the pollen mass, work- 
 ing in between it and the corbicular surface, so that the mass is 
 shoved outward and downward and falls into the cell. As the pollen 
 masses drop, the middle legs are raised and their claws find support 
 upon the edge of the cell. The hind legs now execute cleansing move- 
 ments to remove small bits of pollen which still cling to the corbicular 
 
SUMMARY. 31 
 
 surfaces and hairs. After this is accomplished the bee usually leaves 
 the cell without paying further attention to the two pellets of pollen 
 although some collecting bees Avill stick the head into the cell, possi- 
 bly to assure themselves that the pollen is properly deposited. It has 
 been stated by some (Cheshire, for example) that the spur upon the 
 middle leg is used to help pry the pollen mass from the corbicula. 
 This structure is in close proximity with the mass while the middle 
 leg is pushing downward upon it, but its small size renders difficult 
 an exact estimate of its value in this connection. It is certainly true 
 that the entire planta of the middle leg is thrust beneath the upper 
 end of the pollen mass, but the spur may be used as an entering 
 wedge. 
 
 Pollen masses which have been dropped by the collecting bee may 
 remain for some time within the cell without further treatment, but 
 usually another worker attends to the packing of the pollen shortly 
 after it has been deposited. To accomplish this the worker enters the 
 cell head first, seizes the pollen pellets with its mandibles, breaks 
 them up somewhat or flattens them out, probably mingles additional 
 fluid with the pollen, and tamps down the mass securely in the bot- 
 tom of the cell. As is shown by the analyses of corbicular pollen and 
 of stored pollen, certain substances are added to the pollen after the 
 collecting bee leaves it in the cell. Sugar is certainly added, and it is 
 generally supposed that secretions from some of the salivary glands 
 are mixed with the pollen after deposition. It appears probable that 
 the stored pollen or " beebread " is changed somewhat in chemical 
 composition through the action of the fluids which have been added 
 to it, either during the process of collection, at the time of packing, 
 or later. 
 
 SUMMARY. 
 
 Pollen may be collected by the worker bee upon its mouthparts, 
 upon the brushes of its legs, and upon the hairy surface of its body. 
 When the bee collects from small flowers, or when the supply is not 
 abundant, the mouthparts are chiefly instrumental in obtaining the 
 pollen. 
 
 The specialized leg brushes of the worker are used to assemble the 
 pollen, collecting it from the body parts to which it first adheres and 
 transporting it to the pollen baskets or corbiculse of the hind legs. In 
 this manipulation the forelegs gather pollen from the mouthparts and 
 head; the middle legs, from the forelegs and from the thorax; the 
 hind legs, from the middle legs and from the abdomen. 
 
 The pollen baskets are not loaded by the crossing over of one hind 
 leg upon the other or to any great extent by the crossing of the middle 
 legs over the corbiculse. The middle legs deposit their loads upon the 
 
32 BEHAVIOR OF HONEY BEE IN POLLEN COLLECTING. 
 
 pollen combs of the hind planta?, and the planta?, in turn, transfer the 
 pollen of one leg to the pecten comb of the other, the pecten of one 
 leg scraping downward over the pollen comb of the opposite leg. 
 (See fig. 7.) A little pollen is loaded directly from the middle legs 
 into the baskets when these legs are used to pat down the pollen 
 masses. (See fig. 6.) 
 
 Aside from the foregoing exception, all of the pollen which reaches 
 the baskets enters them from below, since it is first secured by the 
 pecten combs, and is then pushed upward by the impact of the 
 rising auricles, which squeeze it against the distal ends of the tibiae 
 and force it on into the baskets to meet that which has gone before. 
 
 The long hairs which form the lateral boundaries of the baskets 
 are not used to comb out pollen from the brushes of any of the legs. 
 They serve to retain the accumulating masses within the baskets and 
 to support the weight of the pollen, as it projects far beyond the 
 surfaces of the tibia?. 
 
 Pollen grains are moistened and rendered cohesive by the addition 
 to them of fluid substances which come from the mouth. Analyses 
 show that honey forms a large part of this moistening fluid, although 
 nectar and secretions from the salivary glands are probably present 
 also. 
 
 In the process of pollen manipulation this fluid substance becomes 
 well distributed over the brushes of all of the legs. The forelegs 
 acquire moisture by brushing over the mouthparts, and they transfer 
 this to the hairs of the breast and to the middle-leg brushes when 
 they come in contact with them. The middle-leg brushes transmit 
 their moisture to the pollen combs of the hind legs when they rub 
 upon them. All of these brushes also transport wet pollen which 
 has come from the mouthparts and thereby acquire additional mois- 
 ture. The auricles and the planta? of the hind legs become particu- 
 larly wet from this source, since fluid is squeezed from the wet pollen 
 when it is compressed between the auricles and the distal ends of the 
 tibia?. Dry pollen which falls upon the body hairs becomes moist 
 when brought into contact with the wet brushes or with wet pollen. 
 
 During the process of manipulation pollen passes backward from 
 its point of contact with the bee toward its resting place within the 
 baskets. 
 
 Pollen which the collecting bee carries to the hive is deposited by 
 this bee within one of the cells of the comb. As a rule, this pollen is 
 securely packed in the cell by some other worker, which flattens out 
 the rounded masses and adds more fluid to them. 
 
BEHAVIOR OF HONEY BEE IN POLLEN COLLECTING. 33 
 
 BIBLIOGRAPHY. 
 
 Alefeld, Dr. — Vol. 5. Nos. 15 and 16. Eichstadt Bienen Zeitung. Summarized 
 
 in "Die Bienenzeitung in neuer, geschichteter und systematische geordneter 
 
 Ausgabe." Herausgegeben vom Schinid und Kleine : Erste Band, 
 
 Theoretischer Theile. 1861. 
 
 Casteel, D. B., 1912. — The manipulation of the wax scales of the honey bee, 
 
 Circular 161, Bureau of Entomology, U. S. Dept. Agriculture, pp. 15. 
 Cheshire, F. R., 1886. — Bees and bee-keeping ; scientific and practical. Vol. I, 
 
 scientific; II, practical. London. 
 Fleischmann und Zander, 1910. — Beitriige zur Naturgeschichte der Honigbiene. 
 Franz, A., 1906. — In "Unsere Bienen," herausgegeben von Lndwig, A., Berlin. 
 
 pp. [viii]+831. 
 Hommell, R., 1906. — Apiculture, Encyclopedic Agricola, Paris. 
 Phillips, E. F., 1905. — Structure and development of the compound eye of the 
 
 bee. Proc. Acad. Nat. Sci. Philadelphia, vol. 57, pp. 123-157. 
 Sladen, F. W. L., 1911. — How pollen is collected by the social bees, and the 
 part played in the process by the auricle. British Bee Journal, vol. 39, 
 pp. 491^93, Dec. 14. 
 Sladen, F. W. L., 1912. — (a) How pollen is collected by the honey bee. Nature, 
 vol. 88, pp. 586, 587, Feb. 29. 
 
 1912. — (&) Further notes on how the corbicula is loaded with pollen. 
 
 British Bee Journal, vol. 40, pp. 144, 145, Apr. 11. 
 1912.— (c) Pollen collecting. British Bee Journal, vol. 40, pp. 164-166, 
 
 Apr. 25. 
 1912. — (d) How propolis is collected. Some further notes on pollen- 
 collecting. Gleanings in Bee Culture, vol. 40, pp. 335, 336, June 1. 
 1912. — (e) Hind legs of the worker honey bee. Canadian Bee Journal, 
 vol. 20, p. 203. July. 
 Wolff, O. J. B., 1873. — Das Pollen-Einsammeln der Biene. Eichstadt Bienen - 
 Zeitung. 29 Jahrg. Nrs. 22 u. 23, pp. 258-270. 
 
INDEX. 
 
 Page. 
 
 Alefelb on pollen moistening by worker bee 23 
 
 Antenna cleaner of worker bee, figure S 
 
 Auricle of hind planta of worker bee, definition 9 
 
 figure 11 
 
 role and action in pollen collect- 
 ing 16-17, 19, 20-22 
 
 Basket, pollen. (See Corbicula.) 
 
 Brush of foreleg of worker bee, action and role in pollen collecting 13 
 
 figure 8 
 
 hind leg of worker bee, action and role in pollen collecting 16 
 
 middle leg of worker bee, action and role in pollen collecting 14-16 
 
 figure 9 
 
 Brushes of legs of worker bee, use in pollen collecting 8-9 
 
 Bumblebee, moistening of pollen, views of Sladen 23-21 
 
 Ches-hire on process of loading pollen baskets by worker bee IT 
 
 Comb or pecten of hind tibia of worker bee, definition 
 
 figure 77 
 
 role and action in pollen col- 
 lecting 16-19 
 
 Corbicula of worker bee, definition 9 
 
 figure 10 
 
 process of loading 15-22 
 
 Corn, sweet, pollen collecting therefrom by honey bee , 11-13 
 
 Coxae of worker bee, figures S, 9 
 
 Dunbar, Dr. P. B., analyses of corn pollen from plant, from corbiculaa 
 
 of bees, and from hive cells 28 
 
 Femora of worker bee, figures 8,9,10,11 
 
 Fleischmann and Zander on process of loading pollen baskets by worker 
 
 bee ^ IS 
 
 Flowers, variable amounts of pollen from different plants 10-11 
 
 Franz on pollen moistening of worker bee 23 
 
 process of loading pollen baskets by worker bee 17 
 
 Hairs, branched, of honey bee, use in pollen collecting 7-S 
 
 fringing pollen basket, function 20 
 
 unbranched, of honey bee, use in pollen collecting 7, 8 
 
 Hommell on pollen moistening of worker bee 23 
 
 process of loading pollen baskets by worker bee IS 
 
 Honey, use by worker bee for moistening pollen 24,28-29 
 
 Leg, hind, of worker bee, loaded with pollen, figure 22 
 
 Legs, fore, of worker bee, action and role in pollen collecting 12,33 
 
 hind, of worker bee, action and role in pollen collecting 13, 16-1S 
 
 stages in basket-loading process, figure 19 
 
 middle, of worker bee, action and role in pollen collecting 13, 14-16 
 
 of worker bee, action in unloading pollen 30-31 
 
 structures used in pollen collecting- 7-9 
 
 35 
 
36 BEHAVIOR OE HONEY BEE IN POLLEN COLLECTING. 
 
 Page. 
 
 Mandibles of honey bee, action and role in pollen collecting 8,13 
 
 worker bee, use in packing pollen in the cell 31 
 
 Maxilke of honey bee, action and role in pollen collecting 8,13 
 
 Moistening of pollen by bumblebee, views of Sladen 23-24 
 
 honey bee 13,22-29 
 
 Mouthparts of honey bee, action and role in pollen collecting 8, 13 
 
 Nectar, supposed use by worker bee for moistening pollen 24-29 
 
 Palma of foreleg of worker bee, definition 8 
 
 Pecten of hind tibia of worker bee, definition 9 
 
 figure 11 
 
 role and action in pollen collecting 16-19 
 
 Plauta of hind leg of worker bee, definition 3 
 
 figures 10, 11 
 
 structures concerned in pollen collect- 
 ing 9 
 
 middle leg of worker bee, definition 8 
 
 Pollen, chemical composition 26 
 
 collecting by worker bee, bibliography 33 
 
 general statement regarding it 11-13 
 
 summary of process 31-32 
 
 corn, from plant, from corbiculse of bees, and from hive cells, 
 
 analyses to determine nature of moistening fluid 28-29 
 
 moistening by bumblebee, views of Sladen 23-24 
 
 honey bee 22-29 
 
 storage in the hive 29-31 
 
 structures of honey bee concerned in manipulation 7-9 
 
 supply of honey bee 10-11 
 
 unloading process by worker bee 30-31 
 
 Saliva, supposed use by worker bee in moistening pollen 23,29 
 
 Sladen, observations on process of loading pollen baskets* by worker 
 
 bee 18, 20, 21 
 
 views as to pollen moistening by worker bee 23-24,27 
 
 Spur of middle tibia of worker bee, figure 9 
 
 Storing pollen in the hive 29-31 
 
 Structures of honey bee concerned in manipulation of pollen 7-9 
 
 " Sweat glands " of Wolff within hind tibia and planta of worker bee. 
 
 supposed function 24 
 
 Tibia of hind leg of worker bee, modifications and structures for pollen 
 
 collecting 9 
 
 Tibiae of worker bee, figures 8,9,10,11 
 
 Tongue of worker bee, action and role in pollen collecting 8, 13 
 
 Trochanters of worker bee, figures 8, 9 
 
 Wax shears or pinchers, so-called, use in loading pollen by worker bee 7 
 
 Wolff on pollen moistening by worker bee 24 
 
 Zander, Fleischmann and. (See Fleischmann and Zander.) 
 
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UNIVERSITY OF FLORIDA 
 
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