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Tew SC Ue. 2) tires j ~< : : wr er Iw inpi == spi Sc eft ry it | pM Coli i Le as ve o yiet wee ee [| we reeer: 4s, | iS vy eee : ti y? me Pe Vee tebe tobi TLL [OM Net Nvegeres | St PMO atm y ste eY ¥v yeewany, Veuned tliat enwene raat "mM veyatn db ayer yay ee By | Th Ashe Pl TTT At 455 3 } gills Seat AT Ne STITUTE ere. | amt async? mrevenitrver Mitt ttmmet It yatgseste TL i a iy OTT i veel tena TH TCD T ET ee waver sender nme rrr ufone nein WELD tt ¥ , 44 Vere ee iwanseive -* Fahd) LL ee ere aed eT Ad LA <7 : Re nd a = Ap Ow sa few a ~*~ a 3 > ah, ee Oe at ey VEL en Ie eA > in «= CUM, a. | Par wy o2 5 ieee Pay 3 ; OFF a AGRICULTURE, on Cipert oof 3k ‘ ahs wer ht / it Fe B ANATOMY OF THE HONEY BEE. BY © RB. E. SNODGRASS, Agent and Expert. Ly Issuep May 28, 1910. ° Ral, AAS HEINGTON: 9852 2) i Peek ae GOVERNMENT PRINTING ORMEOE. <5 % : As Gene RC anes Age om mea g Lae cs te A ee . : \ sot By wets ie ONES ame Aes TECHNICAL SERIES, No. 18. Cpe eB PARTMENT OF “AGRICULTURE, BUREAU OF ENTOMOLOGY. L. O. HOWARD, Entomologist and Chief of Bureau. THE ANATOMY OF THE HONEY BEE. BY R. E. SNODGRASS, Agent and Expert. Issurp May 28, 1910. WASHINGTON: GOVERNMENT PRINTING OFFICE, 1910. BUREAU OF ENTOMOLOGY. L. O. Howarp, Hntomologist and Chief of Bureau. C. L. Martatr, Assistant Entomologist and Acting Chief in Absence of Chief. R. 8. Cuirton, Hxecutive Assistant. . s W. F. Taster, 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. WesstTeER, in charge of cereal and forage insect investigations. A. L. QUAINTANCE, in charge of deciduous fruit insect investigations. BK. F. PHILvies, in charge of bee culture. D. M. Rogers, in charge of preventing spread of moths, field work. Roiua P. Curriz, in charge of editorial work. MABEL CoucorD, librarian. INVESTIGATIONS IN BEE CULTURE. EK. FE. PHILLIPS, in charge. G. F. WHITE, J. A. NELSON, B. N. Gates, R. HE. SNoperAss, A. H. McCray, agents and experts. ELLEN DASHIELL, preparator. JESSIE E. Marks, clerk. T. B. Symons, collaborator for Maryland. H. A. Surrace, collaborator for Pennsylvania. J. C. C. Price, collaborator for Virginia, 2 LETTER OF TRANSMITTAL. U. S. DeparrMentT or AGRICULTURE, Bureau or Enromoroey, Washington, D. C., October 19, 1909. Sir: I have the honor to transmit herewith a manuscript entitled “The Anatomy of the Honey Bee,” by Mr. R. E. Snodgrass, agent and- expert, of this Bureau. It embodies the results of detailed studies made by Mr. Snodgrass and should prove of value as bring- ing to the bee keeper reliable information concerning an insect of such great economic importance, and also as furnishing a sound basis in devising new and improved practical manipulations. I recommend its publication as Technical Series, No. 18, of the Bureau of Entomology. Respectfully, L. O. Howarp, Entomologist and Chief of Bureau. Hon. JAmrs WILson, Secretary of Agriculture. LV. CONTENTS. MTNLOCNTCULOIEIERE eB remct ee city to nee ee Se AT eee mCenerinexternal siruebure: Ol insectss --o. - 6620 - e seek dhe oaceee cece Lee The head of the bee and its appendages... =... 2... 2.2 ces e cee ee eee foe Wie srnlenmrect the head.) 60029 oe Saat epee ee bese 2. the antennce and their sense organs... ----:.==---.-----.--:--- ane mandimles and their claude s.. .2:osc25. 5.68. .2. oe. kk ee EM RO MEOR ORES E rao 2c ose i Wad CC OM yo ee eed lu ain Bee be ime bnewirienite a tne thorax: o7 0622. y. Jase ee 3. ode eee oe ne Wines AnGwUneir SrieiighiOl, <2 say. 2 oe lene hn pek Sek Shes AEUAVE Iie IS IES et ee Og Pod PD OE SRA” Ss a eee the abdomen, wax glands, and sting.......:-....-..-..- oneaimentary canal and ite clands 2.252.222. So 225-2 Ses es 1. The general physiology of digestion, assimilation, and excretion. Foye BI DES Se gg C03 PG 6 eg eee Drieive, qhinmertaryrcanall: (0 foe Us Seles Jot Cees wee. »SRLTES! Gites PURE AGHSPS SNS) C1 ese ge a ec a ee Peebles PNM TOUVCHV SUCH Re Gehry cia ess x paca doaee oy sv nal tee pe bos tab Wey. atid the GenOC yes 2. 2c lS = ook os ded oe nade node wa 2 peline menvols nyse amd the @yeats.. s2 scrs~ <<). te cees dso Rene LONTOOUGHVC BYStEMUS 22... METS) 68 San soteek olen Co ee en Pear into pian esta eet eyo Oped a ey eh nd os BS oe ig a PLEIN ALE QEPAIS 2-5 54s SSE e eee a wat ob ad g ete eene ata'sn we Explanation of the symbols and letters used on the illustrations... ...- LEST SLUG Coe ANIC (ae ey a ei es RY yk ee ee re ROSS OSE OE aD OS eee ee ee er ee eS Fic. bo b bo wo Nr & bo bo oe 41 ILLUSTRATIONS. . Median longitudinal section of body of worker.. . Diagram of generalized insect embryo...........- . Example of generalized insect mouth parts.....-- . Diagram of generalized thoracic segment........- . Typical insect leg. . Diagram of generalized insect wing and its articulation.............-.. . Diagram of terminal abdominal segments of a female insect and early stage in development of gonapophyses......... . Example of a swordlike ovipositor Head of worker bee worker . Epipharynx and labrum of warker.............. . Sense organs of epiphatyux..) 5.222.522 2-0 . Median longitudinal section of head of worker.... . Dorsal view of ventral walls of body of worker... . Thorax of worker . Lateral view of mesotergum of worker Sh OracieneraarOlnwOnke ieee a eee een . Upper part of left mesopleurum of worker. . . - - . . Wings of Hymenoptern. 72s: 15-2 neers . Basal elements of wings of Hymenoptera - . -..-- . Median section through thorax of drone......... . Internal view of right pleurum of mesothorax of drone. ........---.-- . Legs of worker, queen, and drone.............-- . Claws and empodium of foot of worker........-- . Tarsal claws of worker, queen, and drone. .....- 32. Lateral view of abdomen of worker. ........-.--- Sections of alkaline gland of sting. ............- . Tip of abdomen of worker with left side removed 6 . Heads of worker, queen, and drone.............. . Median longitudinal sections of heads of worker and drone . Antennal hairs and sense orgams................- . Mandibles of worker and drone................. . Internal mandibular elind of worker... <1 98> soe ee ee . Mouth parts of worker . Median section through distal half of mentum and base of ligula of }. Semidiagrammatic view of left side of sting of worker............-...- . Ventral view of sting of worker...............- . Section of small piece of wall of poison sac... .-. oo. > Detailsiof stim olaworker- see eee ae eee Page. _ “Ibo © Www ee a>) bo ILLUSTRATIONS. moMiMen tary Galial Ol WORKEL.... =... =. ooeccbe cl ecc see oss ose cee eee . Details of pharyngeal and salivary glands .......... Be aie . Honey stomach of worker, queen, and drone ..............--.------- . Longitudinal section of honey stomach and proventriculus of queen . . Histological details of alimentary canal of worker ............-----.- . Dorsal diaphragm of drone, from one segment ...........---...----- penal part ot dorsal diaphragm @idrone 2:2. - 2225-5 - ieee. 5. eo . Pericardial chamber of one segment in worker ........---...------- eS etcieal ey scoM won WOLKET.!. 052.2. aite ion cess yee eceh see Se PAG NPM STELl Ol WOLKOR a... nos as ieets cc ke eet tee Ade goes es ae 2 PVGEV His BN STO Ol WOlKOnne ..2 5 Scere. < ktes tes Sorcha Pcie ae ek oe ee . Brain and subcesophageal ganglion of worker -.......-..--.--------- . Horizontal section of compound eye and optic lobe cf worker ....... . Histological details of compound eye of worker ...............-.----- mRenroduchine oreanaiOl GTONG =... -eacsme coos. oo5 ee eee oe ee -meproduetive orean and sting of queen .: .:-. 2. <2 25 ce we seen see . ‘(OF) B]10B pue (2A) JABvOT JO Surjstsuoo Jessea [BSa1op pue ‘(ydqdA pue ydqqd) Uswmopqe jo smsvaydeip [eajueA pue [eBsiop ‘(QI-T ‘ogn4,) Wo sds [wooed ‘(6up1-TdOQ) Woajsks SNOAIoU SulMoYsS ‘1oyxIOM Jo ApoOd o11JUe JO WOLJOIS [BOT}IVA ‘UBIPeM ‘[BUIPNIIsu0 T—T ‘p17 a j é z THE ANATOMY OF THE HONEY BEE. I, INTRODUCTION. The anatomy of the honey bee has been for years a subject of much interest to those engaged in bee keeping both for pleasure and for profit. This interest is due not only to a laudable curiosity to know more of the bee, but to the necessity of such information in order to understand fully what takes place in the colony. All practical manipulations of bees must depend on an understanding of the be- havior and physiology of bees under normal and abnormal circum- stances, and those bee keepers who have advanced bee keeping mo&t by devising better manipulations are those, in general, who know most of bee activity. In turn, a knowledge of bee activity must rest largely on a knowledge of the structure of the adult bee. Studies on the anatomy of the bee have not been lacking, for many good workers have taken up this subject for investigation. The popular demand for such information, however, has induced untrained men to write on the subject, and most accounts of bee anatomy contain numerous errors. This is probably to a greater extent true of the anatomy of the bee than of that of any other insect. Frequently the illustrations used by men not trained in anatomical work are more artistic than those usually found in papers on insect anatomy, and they consequently bear the superficial marks of careful work, but too often it is found that the details are in- accurate. It has therefore seemed the right time for a new presenta- tion of this subject based on careful work. The drawings given in the present paper are original, with the exception of figures 12, 54, and 55, and have been prepared with a thorough realization of the need of more accurate illustrations of the organs of the bee, especially of the internal organs. Mistakes will possibly be found, but the reader may be assured that all the parts drawn were seen. Most of the dissections, moreover, were verified by Dr. E. F. Phillips and Dr. J. A. Nelson, of this Bureau, before the drawings were made from them. An explanation of the abbreviations and lettering is given on pages 139-147. It is hoped that the work will furnish the interested bee keeper with better information on the anatomy of the bee than has hereto- fore been offered to him, that it may provide a foundation for more detailed work in anatomy and histology, and, finally, that it will be 9 10 THE ANATOMY OF THE HONEY BEE. of service to future students of the embryology and physiology of the bee. With this last object in view the writer has tried to sum up under each heading the little that is at present known of insect physiology in order to bring out more clearly what needs to be done in this subject. II. GENERAL EXTERNAL STRUCTURE OF INSECTS. When we think of an animal, whether a bee, fish, or dog, we uncon- sciously assume that it possesses organs which perform the same vital functions that we are acquainted with in ourselves. We know, for example, that an insect eats and that it dies when starved; we realize therefore that it eats to maintain life, and we assume that this involves the possession of organs of digestion. We know that most insects see, smell, and perform coordinated actions, and we recognize, therefore, that they must have a nervous system. Their movements indicate to us that they possess muscles. These assumptions, moreover, are en- tirely correct, for it seems that nature has only one way of producing and maintaining living beings. No matter how dissimilar two animals may be in shape or even in fundamental constitution, their life processes, nevertheless, are essentially identical. Corresponding organs may not be the same in appearance or action but they accom- plish the same ends. The jaws may work up and down or they may work sidewise, but in either case they tear, crush, or chew the food before it is swallowed. The stomach may be of very different shape in two animals, but in each it changes the raw food into a soluble and an assimilable condition. The blood may be red or colorless, con- tained in tubes or not, but it always serves to distribute the prepared food which diffuses into it from the alimentary canal. The situa- tion of the central nervous system and the arrangement of its parts may be absolutely unlike in two organisms, but it regulates the fune- tions of the organs and coordinates the actions of the muscles just the same. Hence, in studying the honey bee we shall find, as we naturally expect to find, that it possesses mouth organs for taking up raw food, an alimentary canal to digest it, salivary glands to furnish a digestive liquid, a contractile heart to keep the blood in circulation, a respira- tory system to furnish fresh oxygen and carry off waste gases, ex- cretory organs for eliminating waste substances from the blood, a nervous system to regulate and control all the other parts, and, finally, organs to produce the reproductive elements from which new indi- viduals are formed to take the places of those that die. The study of anatomy or the structure of the organs themselves is inseparably connected with a study of physiology or the life functions of the animal. While physiology is a most interesting and important subject, and, indeed, in one sense might be said to be Deke ze GENERAL EXTERNAL STRUCTURE OF INSECTS. A ba the object of all anatomical research, yet the mere study of the structure of the organs alone, their wonderful mechanical adapta- tions, and their modifications in different animals forms a most fasci- nating field in itself, and besides this it gives us an insight into the blood relationships and degrees of kinship existing between the multitudes of animal forms found in nature. In the study of com- parative anatomy we are constantly surprised to find that structures in different animals which at first sight appear to be entirely differ- ent are really the same organs which have been simply changed in a superficial way to serve some new purpose. For example, the front wing of a bee and the hard shell-like wing cover of a beetle are fundamentally the same thing, both being front wings—that of the beetle being hardened to serve as a protection to the hind wing. Again, the ovipositor of a katydid and the sting of a bee are identical in their fundamental structure, differing in details simply because they are used for different purposes. Hence, in the study of anat- omy we must always be alert to discover what any special part cor- responds with in related species. In order to do this, however, it is often necessary to know the development of an organ in the embryo or in the young after birth or after hatching, for many complex parts in the adult have very simple beginnings in an imma- ture stage. Thus it becomes evident that the structural study of even one organism soon involves us in the subjects of anatomy, physiology, and embryology, and, if we add to this a study of its senses, its behavior, and its place in nature, the field enlarges without limit. The student of the honey bee realizes that a lifetime might be spent in exploiting this one small insect. The differences between animals are much greater on the outside than on the inside. In the descriptions of the organs of the honey bee anyone will know what is meant by the “alimentary canal,” the “nervous system,” or the “respiratory system,” but the external parts are so different from those of animals with which we are more familiarly acquainted that no general reader could be expected to know what is meant by the names apphed. Moreover, the bee and its allies are so modified externally in many ways that, at first sight, their parts look very different even from those of other insects. Hence, we shall give a preliminary account of the external structure of insects in general, for it is hoped that the reader will then more easily understand the special structure of the honey bee, and that the application of the terms used will appear more reasonable to him. Since all animals originate in an egg, the change into the adult involves two different processes: One is growth, which implies merely an increase in size, the addition of material to material; the other is development, which means change in shape and the produc- 12 THE ANATOMY OF THE HONEY BEE. tion of a form with complex organs from the simple protoplasmic mass of the egg. The part of development that takes place in the eggshell is known as embryonic development, that which takes place subsequent to hatching is known as postembryonic development. In insects there are often two stages in the postembryonic development, an active one called the larval stage and an inactive one called the pupal stage. During the first of these the young insect is termed a larva; during the second, a pupa. When there is no resting stage the immature creature is often called a nymph. The final and fully de- veloped form is an adult, or imago. Since this paper is to deal only with the anatomy of the adult, the attractive fields of embryonic and postembryonic development must be passed over, except for a few statements on fundamental embryonic structure, a knowledge of which is necessary to a proper understanding of the adult anatomy. When the embryo, in its course of development, first takes on a form suggestive of the definitive insect, it consists of a series of segments called metameres, or somites, and shows no differentia- tion into head, thoracic, and abdominal regions. Typically, each segment but the first is provided with a pair of latero-ventral appendages, hav- ing the form of small rounded protuberances. These appendages are of different sizes and take on different shapes in different parts of the body, for some of them are destined to form the ye antenni, some the mouth parts, others the legs An~ and perhaps the cerei, while the rest of them Fig. 2. Diagram of 4 remain very small and finally disappear. What generalized insect em- bryo, showing the see- we know of the embryology of insects is based mentation of the head, 2 thoracic, and abdom. ON the observations of a number of men who inal regions, and the have worked mostly on the development of dif- segmental appendages. y : e ; ferent species. Their observations are not all alike, but this is probably due in large part to the fact that the embryos of different insects are not all alike. Embryos have a very provoking habit of skipping over or omitting little and yet im- portant things in their development, but fortunately they do not all omit the same things. Therefore, by putting together all the reliable information we possess, we can make up an ideal embryo which would be typical of all insects. Such a generalized embryo is represented diagrammatically by figure 2. The first six or seven metameres very early begin to unite with one another and continue to fuse until their borders are lost. These consolidated embryonic segments form the head of the adult insect. GENERAL EXTERNAL STRUCTURE OF INSECTS. 13 - Observers differ concerning the fate of the seventh segment, but it is most probable that a part of it fuses with the sixth segment, thus taking part in the formation of the head, and that a part of it forms the neck or some of the neck plates of the adult. The appendages of these first seven segments form the antennz and mouth parts, except one or two pairs that disappear early in embryonic life. It is not certain that the first segment ever possesses appendages, but from it arise the large compound eyes and appar- ently also the upper lip, or labrum (Zm). The appendages of the second segment form the feelers, or antenne (/Ant) of the adult, those of the third (2An¢) disappear in insects, but they correspond with the second antennz of shrimps and lobsters. The appendages of the fourth segment form the mandibles (J/d). Those of the fifth segment (S/in), when present, fuse with a median tonguelike lobe (Zin) of the following segment, and the three constitute the hypopharynx, or lingua of the adult. The next pair (/J/7) form the maxille, while the last (24/7), or those of the seventh segment, coalesce with each other and constitute the adult labium, or lower lip. The bodies of the head metameres fuse so completely that it is impossible to say positively what parts of the adult head are formed from each. The last, as already stated, possibly takes part in the formation of both the head and the neck. Some embryologists at- tribute the plates which usually occur in this region to the last em- bryonic head segment, while others believe they come from the next segment following. Sometimes these plates are so well developed that they appear to constitute a separate segment in the adult, and this has been called the microthorax. If this name, however, is given to the embryonic segment from which these plates are said to be derived, it must be remembered that it is not “thoracic” at all and belongs partly to the head. The name cervicum has been ap- plied to the neck region with greater appropriateness since it does not imply any doubtful affiliation with adjoining regions. What we really need, however, is not so much a name as more information concerning the development of the rear part of the head and the neck plates in different insects. The next three segments remain distinct throughout life in nearly all insects, but, since they bear the legs and the wings, they become highly specialized and together constitute the thorav. The indi- vidual segments are designated the prothorax, the mesothorax, and the metathorax. 'The legs are formed from the embryonic ap- pendages (fig. 2, /L, 2Z, 3L) of these segments, but the wings are secondary outgrowths from the mesothorax and metathorax and are, hence, not appendages in the strict embryological sense. The remaining segments, nearly always 10 in number, constitute the abdomen. The appendages of these segments, except possibly 14 THE ANATOMY OF THE HONEY BEE. those of the tenth, disappear early in embryonic life in all inseets, except some of the very lowest species, in which they are said to form certain small appendages of the abdominal segments in the adults. An adult insect is often described as being “ divided ” into a head, a thorax, and an abdomen, but this is not true in most cases. While all insects consist of these parts, the divisions of the body are usually not coincident with them. The prothorax in the adult is separated from the head by the neck and is very commonly separated from the mesothorax by a flexible membranous area. On the other hand, the mesothorax and metathorax are almost always much more solidly at- tached to each other, while, in most insects, the metathorax is solidly and widely joined to the first abdominal segment, though in the flies these latter two segments are usually separated by a constriction. In such insects as ants, wasps, and bees a slender, necklike peduncle occurs between the first and second segments of the abdomen, the first being fused into the metathorax so that it appears to be a part of the thorax. This is the most distinctive character of the order Hymenoptera, to which these insects belong. The body wall of insects is hard on account of the thick layer of chitin which exists on the outer side of the true skin. Chitin is a sub- stance similar to horn, being brittle, though tough and elastic. It gives form and rigidity to the body and affords a solid attachment for the muscles within, since insects have no internal framework of bones such as vertebrate animals have. The skin between the segments is soft and unchitinized and thus forms a flexible intersegmental mem- brane which is often very ample and, in the abdomen, allows each seg- ment to telescope into the one in front of it. The chitin of each segment is not continuous, but is divided into plates called sclerites. The most important of these are a tergum above and a sternum below, but, in the case of the thorax, these two plates are separated on each side by another called the plewrum, which lies between the base of the wing and the base of the leg. Pleural plates are sometimes present also on the abdominal segments. These principal segmental plates are usually separated by membranous lines or spaces, which permit of more or less motion between them. Such lines are called sutures in entomology, though strictly this term should be applied only to the lines of fusion between adjoining parts. The terga, pleura, and sterna of each segment are furthermore subdivided into smaller sclerites, which may be termed ¢ergztes, pleu- rites, and sternites, respectively. The sutures between them are sometimes membranous also, but most frequently have the form of impressed lines or narrow grooves. In such cases they are generally nothing more than the external marks of ridges developed on the inside of the body wall to strengthen the parts or to give attachment to muscles. Since these sutures are conspicuous marks on the outside GENERAL EXTERNAL STRUCTURE OF INSECTS. 15 of an insect, they are usually regarded as morphologically impor- tant things in themselves, representing a tendency of the tergum, pleu- rum, or sternum to separate into smaller plates for some reason. The truth about them would appear to be just the opposite in most cases— they are the unavoidable external marks of an internal thickening and strengthening of the plates. In a few cases they may be the confluent edges of separate centers of chitinization. Hence, most. of the sutural lines in insects appear to signify a bracing or solidifying of the body wall rather than a division of it. Since the body wall of insects is continuous over all the surface it contains no articulations of the sort that occur between the bones in the skeleton of a vertebrate. Although insects and their allies be- long to the class of animals known as the Articulata, yet an articu- late articulation is simply a flexibility—two chitinous parts of the exoskeleton are movable upon each other simply by the intervention of a nonchitinized, flexible, membranous part. While there are often special ball-and-socket joints developed, these are always produced on the outside of the membranous hinge and simply control. or limit the movement of the articulation. The head of an adult insect is a thin-walled capsule containing the brain, the ventral head ganglion of the nervous system, the pharynx and anterior part of the csophagus, the tracheal tubes, and the muscles that move the antenne and the mouth parts. Its shape varies a great deal in different insects, being oval, globular, elongate, or triangular. In some it is flattened dorso-ventrally so that the face is directed upward and the mouth forward, but in most, including the bee, it is flattened antero-posteriorly so that the face looks for- ward and the mouth is directed ventrally. In a few it is turned so that the face is ventral. The walls of the head are usually divided by sutures into a number of sclerites, which in general are located and named as follows: The movable transverse flap forming the upper lip is the Jabrum. Above it is a sclerite called the clypeus, which is a part of the solid wall of the head and carries the anterior articulations of the mandibles. The clypeus is sometimes divided transversely into an anteclypeus (“clypeus anterior,’ “ epistoma ”) and into a post-clypeus (“clypeus posterior”). Above the clypeus is the front, a plate usually occupying the upper half of the face between the compound eyes and carrying the antenne. The top of the head is called the vertex, but does not constitute a separate scle- rite. The sides of the head below the compound eyes are often sepa- rated by sutures from the anterior and posterior surfaces and are known as the gene. The back of the head is formed by the occiput, which surrounds the large opening or foramen magnum that leads from the cavity of the head into that of the neck. The parts pos- terior to the genx, carrying the posterior mandibular articulations, 16 THE ANATOMY OF THE HONEY BEE. are sometimes separated from both the occiput and the gene and are known as the postgene. In a few insects, especially beetles, one or two median plates occur in the ventral wall of the head posterior to the base of the labium. These are the gular sclerites. Finally, small plates are sometimes found about the bases of the antenne and be- tween the bases of the mandibles and the gene. The latter have been termed the trochantins of the mandibles. The term epicranium is often used to include all the immovable parts of the head, but is frequently applied only to the dorsal parts. Most of these sclerites preserve a pretty definite arrangement in the different orders, and they are probably homologous throughout the entire insect series, though they are in some cases very much distorted by special modi- fications and are often in part or wholly obliterated by the disap- pearance of the sutures. Embryologists are coming to the conclu- sion that the sclerites of the head have no relation to the primitive segments. The latter very early consolidate into a head with a con- tinuous wall, while the sutures defining the sclerites are formed later. Some of the older entomologists were led, from a study of the sclerites, to suppose that the head consisted of a number of seg- ments, but it has been shown that these anatomical segments do not correspond with the embryonic ones. The appendages growing from the front of the face are the antenne (fig. 9A, Ant) or “ feelers” and consist of a series of joints or segments. At the lower edge of the face is the front lip or labrum (fig. 9A, Lm), behind which are the median epipharyna, the paired mandibles (Id) and maville, the median hypopharynx, and the /abiuvm or under lip. All these organs together constitute what are known as the mouth parts or trophi. They vary greatly in shape and appearance in different insects according to the nature of the food, but their typical form is usually taken to be that shown by the lower insects which feed on solid food and have biting mouth parts. Figure 3, representing the jaws and lips of the common black cricket, is given as an example of generalized insect mouth parts. The labrum (fig. 9A, 2m) is usually a simple transverse flap in front of the mouth, being developed, as already shown, from a similarly situated lobe on the first segment of the embryo (fig. 2, Lm). The epipharynx (fig. 19, HX phy) is a sort of dorsal tongue, and is situated on the membrane leading into the mouth from behind the labrum. The mandibles (figs. 3A; 9A, M/d) are typically formed for biting, being heavy organs situated immediately behind the labrum and working sidewise on a hinge articulation with the head. Their cutting edges are usually notched and toothed, though smooth in the worker bee. GENERAL EXTERNAL STRUCTURE OF INSECTS. Et The maxille (fig. 3 B and B) are complicated appendages in their typical form. Each consists of a principal piece called the stipes (SZ), which is hinged to the head by means of a smaller basal piece, the cardo (Cd). Terminally the stipes bears an outer lobe, the galea (Ga), and an inner lobe, the lacinia (Zc). On the outer side, at the base of the galea, it carries a jointed appendage called the maadlary palpus (Pip). The hypopharynx (fig. 3 C and D, Hphy) is a median, ventral, tonguelike organ, called also the /ingua, situated either on the upper surface of the labium or on the membrane between this organ and the mouth. It is de- veloped principally from a median lobe of the head of the embryo behind the mouth (fig. 2, Zn), but some entomol- ogists claim that it is compounded of this lobe and two smaller lateral ones developed from the appendages of the fifth embryonic head segment (fig. 2, Slin), the super- lingue. The labium (fig. 3 C and D) consti- tutes the under lip 1 Fic. 38.—Example of generalized insect mouth parts, from of the adult, but it common black cricket (Gryllus pennsylvanicus) : A, man- : dibles; B, B, maxillw, ventral view; C, labium or second 1S formed from the maxille, ventral view; D, labium, lateral view. two appendages of the seventh segment in the embryo, which fuse with each other. For this reason it is often called the second maville. It consists of a basal submentum (Smt) bearing the mentum (Mt), which in turn carries three parts, a median ligula (Lg) and two lateral palpigers (Piq). The latter support the labial palpi (Pip), while the ligula bears four terminal lobes, of which the median ones are called the glosse (Gls) and the lateral ones the paraglosse (Pgl). If we should cut the labium into two parts along its midline we should see that even in the adult stage each half is very similar to one maxilla. The only discrepancy to be noticed in the example given (fig. 3) is that there 22181—No. 18—10 2 18 THE ANATOMY OF THE HONEY BEE. is no maxillary palpiger, but many insects possess a corresponding part in the maxilla, frequently distinguished as the palpifer. The neck or cervicum is usually a short membranous cylinder which allows the head great freedom of motion upon the thorax. In nearly all insects its lateral walls contain several small plates, the cervical sclerites, while, in many of the lower species, dorsal, ventral, and lateral sclerites are present and highly developed. As already stated, the origin of these plates is doubtful. Some entomologists would derive them from the prothorax, others think they come from the last head segment, while still others think that they represent a separate segment. Only pure anatomists, however, entertain this last view and call this supposed segment the ‘“ microthorax,” for embryologists have not yet reported a metamere between the labial segment and the prothoracic segment. Most embryologists who have studied the subject admit that some of the cervical sclerites may be formed from the last embryonic head somite which carries the labium and probably forms a part of the back of the head. Therefore, if it is desirable to retain the word microthorar as a name for a true segment, it can be applied only to this labial metamere.* The thorax, as has already been stated, is a distinct anatomical region of the body rather than a “ division” of the body, since it car- ries both the legs and the wings and contains the large muscles for each. Since the prothorax does not possess wings, it is not so highly developed otherwise as the two wing-bearing segments, and is, indeed, generally reduced in some ways, some of its parts being frequently rudimentary. Therefore we shall base the following description of a typical segment on the structure of the wing-bearing segments. A typical thoracic segment, then, presents four surfaces, as does also the entire body. These are a dorsum above, a venter below, and a latus® on each side. From these names we have the terms “ dorsal,” “Tn a former paper on the thorax of insects (Proc. U. S. Nat. Mus., XXXVI, 1909, pp. 511-595) the writer probably drew a too definite conclusion on the subject of the “microthorax.” The origin of the neck sclerites has probably never yet been actually observed. Comstock and Kochi (Amer. Nat., XXXVI, 1902, pp. 18-45), in summarizing the segmentation of the head, accredited the gular and cervical sclerites to the labial segment, but did not recognize the latter as taking part in the formation of the true head capsule. Riley, how- ever, in his study of the development of the head of a cockroach (Amer. Nat., XXXVIIT, 1904, pp. T77-810), states that in Blatta the labial segment does form a part of the back of the head and that the posterior arms of the tentorium are derived from it. Bé6rner (Zool. Anz., XXVI, 1903, pp. 290-315) and Crampton (Proc. Acad. Nat. Sci. Phila., 1909, pp. 8-54) believe that the cervical sclerites are derived principally from the prothoracic segment. The notion that they constitute a separate segment, the “ microthorax,”’ equivalent to the maxilliped segment of the centipedes, has been elaborated principally by Verhoeff in his numerous writings on the Chilopoda and Dermaptera. >The writer introduces this word here because he knows of no other term applied to the side of the segment in this sense. af GENERAL EXTERNAL STRUCTURE OF INSECTS. 19 “ventral,” and “lateral.” The chitinous parts of the dorsum con- stitute the tergum; of the venter, the sternum, and of the latus, the pleurum. The tergum of the wing-bearing segments usually consists of two plates—a front one or true notwm (fig. 4, NV) carrying the wings, and a posterior one, which the writer has termed the postnotum or pseudonotum (PN), having no connection with the wings. The first is often more or less distinctly marked into three transverse parts called the prescutum (Psc), scutum (Sct), and sev- tellum (Scl). In such cases the exposed part of the postnotum is called the postscutellum (Pscl). From either the anterior or the pos- terior margin of the tergum, or from both, a thin transverse plate projects downward into the interior of the thorax for the attachment of muscles. These plates are the phragmas (Aph and Pph). The notum supports the wing on each side by two small lobes, the anterior and posterior notal wing processes (ANP and PNP). Behind the latter is the attachment of the axillary cord (AwC) or basal ligament of the wing. A large V-shaped ridge on the under surface of the notum hav- ing its apex forward is the “ entodor- sum.” (A _ better name would be entotergum.) The pleurum consists principally of two plates, the episternum (fig. 4, L'ps) Fic. 4.—Diagram of generalized and the epimerum (E'pm) lying before i ualie ar i and behind a vertical groove, the pleural suture (PS), which extends from the pleural coxal process (CxvP) below to the pleural wing process (WP) above. The pleural suture marks the position of a heavy internal ridge, the pleural ridge or entopleurum. The epi- merum is connected with the postnotum (PV) behind the base of the wing. These parts occur in almost all insects. In some of the lower ones another plate is present in front of the episternum which may be called the preepisternum, (Peps).* Lying along the upper edge of “Objection may be made to the use of the term “ preepisternum” on the ground that it combines a Latin prefix with a word compounded of Greek ele- ments. The same may be urged against ‘‘ prephragma,” “ postphragma,” ‘ pre- paraptera,” and ‘“ postparaptera,”’ words introduced by the present writer in a former paper on the thorax (Proc. U. S. Nat. Mus., XXXVI, 1909, pp. 511-595). However, we are barred from making up equivalent terms with the Greek pre- fixes pro and meta because these are used to designate the first and the third 20 THE ANATOMY OF THE HONEY BEE. the pleurum and associated with the under surface of the wing base are several small plates known as the paraptera (P).* Two lie above the episternum in front of the pleural wing process and are the episternal paraptera or preparaptera (1P and 2P), while one or occasionally two are similarly situated behind the wing processes and are the epimeral paraptera or postparaptera (3P and 4P). The preparaptera afford insertion for the muscle concerned in the exten- sion and pronation of the wing. The cova (Cx), or basal segment of the leg, is hinged to the seg- ment by a dorsal articulation with the pleural coxal process (CwP), and by a ventral articulation (ZC) with a plate called the trochan- tin (Tn) lying in front of it and connected above with the lower end of the episternum (/’ps). Hence, while the leg is of course con- tinuous all around its base, by means of membrane, with the body- wall, its movement is limited to a hinge motion by these two special articulations of the chitin. The sternum or ventral plate of the segment is not so complicated as are the tergum and pleurum. It is often divided transversely into three parts, however, and some authors say typically into four. These parts have been named the presternum (Ps), sternum proper (8), segments of the thorax or their respective parts. Entomologists have already established the system of referring a part to the front or back of any individual segment by the Latin prefixes pre (or pre) and post as used in “ prescutum,” “presternum,” ‘* postscutellum,” and ‘ poststernellum.” Furthermore, pre and post are so indiscriminately used in English combined with Latin, Greek, and even Anglo-Saxon words that they may be regarded as general property. Hence, in order not to sacrifice an anatomical system, which certainly needs to be fostered in every way, the writer has preferred to sacrifice strict gram- matical rules by applying pre and post, regardless of the origin of the noun in the case, to designate anterior and posterior parts of the same segment. We already use such hybrid terms as “ presternum,” “ mesotergum,” and ‘* meta- tergum.” The name “ preepisternum”’ has been applied by Hopkins (Bul. 17, Pt. I, technical series, Bur. Ent., U. 8. Dept. Agr., 1909) to a part of the mesepister- num of Dendroctonus—a plate apparently not homologous with the preepisternal element of the thorax in primitive insects. @The name “parapterum” is taken from Audouin’s term paraptere (Ann. des Sci. Nat., I, 1824, pp. 97-185, 416-482), and its application, as used by the present writer, is based on Audouin’s definition given in his Chapter III, “ Considerationes generales sur le Thorax,” where he says (p. 122): “ Finally there exists a piece but little developed and seldom observed, connected with both the episternum and the wing. It is always supported by the episternum and is sometimes prolonged ventrally along its anterior margin, or again, becoming free, passes in front of the wing and may even come to lie above the base of the latter. At first we designated this sclerite by the name of Hypoptere but on account of its change of position relative to the wing base we now prefer the name of PARAPTERE.” The first part of his description leaves no doubt that Audouin referred to the little pleural plate beneath the front of the wing which is usually very inconspicuous except in carefully dissected GENERAL EXTERNAL STRUCTURE OF INSECTS. 21 sternellum (Sl), and poststernellum (Psl). In some of the lower insects a plate (xv) occurs at each side of the presternum or of the sternum which seems to fall in line with the preepisternum of the pleurum. This has been variously called a part of the presternum, the cowosternum, an accessory sternal plate, and the sternal laterale. The inner surface of the sternum carries a large two-pronged process called the furca or ento- sternum. This plan of structure for the mesothorax and the metathorax prevails throughout all insects. The honey bee probably presents the greatest de- Emp la parture from it, but even Se ae ea bere the modification consists principally of a suppression of the sutures of the pleurum resulting from a condensation of the parts. The leg (fig. 5) of an adult insect consists of a number of joints or segments. It is attached to the body, as just described, by a thick specimens. In such preparations, however, one finds that there are in most cases two sclerites here instead of one, and, furthermore, that one or ocea- sionally two others are similarly situated beneath the rear part of the wing base behind the pleural wing process. The present writer has, therefore, made the term “ paraptera” cover this whole row of little plates, distinguish- ing those before and those behind the pleural wing process by the designations given above. In the latter part of Audouin’s definition it would seem that he may have confused the rudimentary tegula as it exists in some insects with the parapte- rum, but even this is not probable since he says it is always connected with the episternum, which is never true of the tegula. In his description of the thorax of beetles, Dytiscus, Carabus, Buprestis, and Curculio, it is evident that he regards the anterior upper part of the episternum as the parapterum fused with the latter plate. In fact, in each case he definitely states that such is the case and, in describing Dytiscus circumflerus, he says (p. 420): ‘The episternum, the parapterum, and the epimerum all fuse dorsally and constitute a support for the wings and tergum.” While Audouin is undoubtedly mis- taken in this homology, especially in the mesothorax, he at least shows that his “ paraptére” is a part of the pleurum. Hence modern writers such as Packard and Folsom who make the term “ paraptera’’ synonymous with “tegule” are certainly wrong. The tegula is a dorsal scale or its rudiment at the humeral angle of the wing, while the parapterum is a co-existent scle- rite below this part of the wing base. The present writer agrees with Comstock and Kellogg, who, in their Elements of Insect Anatomy (first edition), define the little sclerite in front of the base of the wing in the locust, articulated to the dorsal extremity of the episternum, as the ‘“ parapteron,” though in this insect there are here really two of these parapteral plates instead of one. oe THE ANATOMY OF THE HONEY BEE. basal joint called the cova (Cw). Beyond this is a smaller joint called the trochanter (77), this is followed by a long and strong segment, the femur (2), which extends outward from the body, while bending downward from its distal end is the long and slender tibia (7b), followed finally by the foot, or tarsus (Tar). The tarsus itself consists typically of five small segments of which the last bears a pair of claws (Cla). The under surfaces of the tarsal joints are often provided with small cushions or pads called pulvilli. Those between the claws are generally specially prominent and are called the empodia (Imp). The leg varies greatly in shape in different in- sects but usually preserves all of these parts. The segments of the tarsus, however, are frequently reduced in number. The adult wing is a thin expanse of membrane supported by hollow branching rods called veins. It originates as a hollow outgrowth of the body-wall, but soon becomes flattened out dorso-ventrally and the Fic. 6.—Diagram of generalized insect wing and its articulation to first plate (N) of the tergum. contained trachez or air tubes mark out the courses of the veins. These veins form various patterns in different insects, but they can all be derived by modification from one fundamental plan. This plan is shown diagrammatically by figure 6. The first vein, which usually forms the anterior margin of the adult wing, is the costa (C). The next vein is the subcosta (Sc), which in typical cases divides into two branches (Sc, and Sc,). The third and usually the principal vein is the radius (f#). It divides dichotomously into five branches (?, to &,), the anterior branch of the first fork remaining single. The next vein is the media (J/), which forms four branches (J/, to M,). The fifth is the cubitus (Cw), which again is two-branched. The remaining veins are called the ana/s and are designated indi- vidually as the first anal (1A), second anal (2A), ete. Several cross-veins of common recurrence should be noted. The first is situated near the base of the wing between the costal and subcostal veins and is known as the humeral cross-vein. A second GENERAL EXTERNAL STRUCTURE OF INSECTS. 23 occurs between the radius and the media near the center of the wing and is called the radio-medial cross-vein. Another one, the medio- cubital, is similarly located between the media and the cubitus, while a fourth, called the median, occurs between the second and third branches of the media. The areas of the wing surface inclosed by the veins, the cross-veins, and the margins of the wing are known as the cells. A great many different names are applied by different entomolo- gists to the veins of the wings, both of the same and of different insects. The nomenclature here given is the one first consistently applied by Comstock and Needham and now used by a large number of entomologists working in different orders of insects. The wing is articulated at its base (except in mayflies and dragon- flies) to the anterior and posterior wing protesses of the notum (fig. 6, ANP and PNP) and to the wing process of the pleurum (fig. 4, WP) by several small articular sclerites called axillaries. ‘Two of these, the first (7A) and the fourth (44x), form a hinge with the anterior and the posterior notal wing processes, respectively, while the second (2A) articulates below with the wing process of the pleurum, constituting thus a sort of pivotal element. The third avxil- lary (Aw) intermediates between the bases of the anal veins and the fourth axillary—except when the latter is absent (as it is in nearly all insects except Orthoptera and Hymenoptera), in which case it articulates directly with the posterior notal process. The thin mem- brane of the wing base may be called the axillary membrane (Awvd). On its anterior edge is a hairy pad, the tegula (77), which is some- times a large scale overlapping the humeral angle of the wing. The posterior margin of the axillary membrane is thickened and may be valled the axillary cord (AwC) or basal ligament of the wing. The base of the costa is not directly associated with any of the axillaries, but is specially connected by tough membrane below with the episternal paraptera. The subcosta abuts against the end of the curved neck of the first axillary. The radius is either attached to or touches upon the anterior end of the second. The media and cubitus are usually associated with each other at their bases and also more or less closely with one or two median plates (m) in the wing base. These plates, however, are not of constant shape and occur- rence as are the articulating axillaries. The anals are generally attached to the outer end of the third axillary, which acts as a lever in the folding of the wing. A few insects have a generalized wing almost identical with the diagram (fig. 6), but most of them depart from it in varying degrees. Few go so far, however, as the honey bee, whose venation is very different, but yet the fundamental basal structure is the same even 24 THE ANATOMY OF THE HONEY BEE. here, as will be shown in the special description of the wing of the bee. The abdomen consists almost always of 10 segments. There are hever any more than this number well developed in adult insects, and if there are fewer the reduction is due to a modification of the ter- minal segments to accommodate the external organs of reproduction. The posterior opening of the alimentary canal is at the end of the tenth segment, which carries also two small appendages at the sides of the anus. These are called the cerci (fig. 8, Cer). In some insects they are short, styletlike processes, in others they are long and many jointed, while in many they are absent. The cerci are supposed to be developed from the embryonic appendages of the tenth segment, although, on the other segments, these appendages disappear before the embryo hatches, except in some members of the lowest wingless order of insects, which have a pair of cercuslike appendages on each segment of the abdomen. Each abdominal segment presents a tergum above and a sternum below; the former usually also reaches far down on the sides and overlaps the edges of the sternum. In some insects one or more small pleural plates intervene between the tergum and the sternum, but the abdominal pleura are never developed in any way suggestive of a thoracic pleurum. Very frequently there is present an upper pleural plate, or epipleurite, adjoining the edge of the tergum and a lower, or hypopleurite, adjoining the edge of the sternum. The line separating these two sclerites, however, is horizontal and can not correspond with the vertical suture of a thoracic pleurum between the episternum and the epimerum extending from the base of the leg to the base of the wing. The most complicated structures on the abdomen are the external organs of reproduction. In the male these serve as clasping organs and take on a great variety of forms in different species. The organs in the female form an ovipositor and are of much more definite and constant structure. The ovipositor (fig. 8), in its most perfect development, consists of three pairs of long, closely appressed bladelike processes called gonapophyses (14, 2G, 3G). These six pieces fit neatly together and form an organ by means of which the female makes a hole in the ground or in the bark of a tree, or punctures some other insect, and then places her eggs in the cavity thus produced. An interesting fact in this connection is that the sting of a wasp or bee is simply a modi- fied ovipositor. This can be proved by a comparison of the organs themselves or by a study of their development. Each is formed from six little peglike processes that grow out from the sterna of the eighth and ninth abdominal segments of the larva or young soon after hatch- GENERAL EXTERNAL STRUCTURE OF INSECTS. 25 ing (fig. 7, 7G, 2G, and 3G). At first there is only one pair of these processes on each of the two segments, but those on the ninth soon split each into two, thus producing two pairs on this segment. The opening of the oviduct (Ov@) is on the eighth segment between the bases of the first gonapophyses. The ovipositor of the longhorned grass- hopper, shown by figure 8, may be taken as a typical example of this organ. The median pair of gonapophyses on the ninth segment (2G) remain slender and fuse at their bases into a small bulblike swelling open below (SAB). The pair from the eighth segment (/G') form two long blade- age = . 0 >< ~ “Cer \ . . ° ° 7 . \ \ like pieces, which fit by sliding articula- An 3G ] a eae ees yp. Hie. 1.—Diagram of terminal tions upon the lower edges of the corre SET ce ance cE A” ie: sponding second gonapophyses (2G). The male insect and early stage in 5 ae eS development of gonapophyses first can therefore be worked back and oer ind: sey drein forth while they are braced and held in — which is formed the ovi- Bap : ieus : positor of most insects and position by the second pair. The third fee ink AE Wepe ae EES, gonapophyses (3G'), or the outer pair of the ninth segment (the left one in figure 8 is shown as if cut off near its base), form two long flat blades which are closely appressed against the outer surfaces of the others. In the detailed study of the bee it will be shown how closely the structure of the sting corre- sponds in every way with that of this ovipositor. cephalus sp.), illustrating the fundamental similarity of structure with the sting of the bee, fig. 36. Some entomologists have supposed that the original two pairs of gonapophyses represent the embryonic appendages of the eighth and ninth segments, and they would thus establish a homology between the ovipositor or sting and the legs and mouth parts. It has been shown, however, that the true appendages of the abdominal segments disappear in embryonic life while the gonapophyses appear much later, during early nymphal or larval life. Furthermore, each pair 26 THE ANATOMY OF THE HONEY BEE. of gonapophyses arises in a median depression on the ventral side of the segment while the true appendages are latero-ventral. Hence, the evidence is very much against this theory and the gonapophyses appear to be special secondary processes of the body wall. All insects do not have ovipositors of the sort described above. Flies, beetles, moths, and butterflies do not. Such insects simply drop their eggs from the orifice of the oviduct or deposit them in masses upon the external surfaces of various objects. In some of the flies, however, the terminal segments are long and tubular and entirely telescoped into one another. They are hence capable of being protruded in the form of a long tapering tube having the open- ing of the oviduct near the tip. This enables the insect to deposit its egos in deep crevices, but the structure is not a true ovipositor—it is simply the abdomen itself stretched out. ; Insects breathe through a series of small holes situated along each side of the body. These breathing apertures are called spiracles and they lead into a system of internal air tubes called trachew. There are nearly always 10 spiracles present on each side of the body. Two are located on the thorax, the first between the prothorax and the mesothorax, the second between the mesothorax and the metathorax, while the other eight are situated on the first eight abdominal seg- ments. Some embryologists believe that the spiracles of the pro- thorax move forward in early embryonic life and unite with each other in front of the hypopharynx to form the salivary opening, their trachez constituting the salivary ducts. After this review of the general external structure of insects we may proceed to a more detailed account of the parts and organs of the honey bee. III. THE HEAD OF THE BEE AND ITS APPENDAGES. The head of an insect, as already explained, is a composite organ formed of six or seven primitive segments, each of which, except the first, typically bears a pair of appendages (fig. 2). The antenne are developed from the embryonic appendages of the second segment, the mandibles from the fourth, the maxille from the sixth, and the second maxille, or labium, from the seventh. The appendages of the third segment disappear in early embryonic life while those of the fifth segment, when the latter is present, fuse with a median tonguelike lobe of the next segment to form the hypopharynx of the adult. 1. THE STRUCTURE OF THE HEAD. The general appearance and outline of the head of a worker bee are shown from before and behind by figure 9, A and B. In facial view the head is triangular, with the apex below. The side angles THE HEAD OF THE BEE AND ITS APPENDAGES. Ot are rounded and capped by the large compound eyes (/’). In the opposite direction the head is very much flattened, the greatest diame- ter being crosswise through the middle of the eyes. The face is con- vex, while the posterior surface is somewhat hollowed out and fits snugly upon the anterior end of the thorax. The large lateral eyes (fig. 9 A, #’) are called the compound eyes, because each is composed of a large number of separate eye elements forming the little hexagonal facets visible on the surface. All of these facets together constitute the cornea, or the transparent outer surface of the eye, which in the bee is densely clothed with long hairs. The dark color of the eye is located in the deeper parts, but these will be described in the section dealing with the nervous system. On the Fic. 9.—A, front view of head of worker bee with mouth parts (Prb) cut off a short distance from their bases; B, corresponding view of posterior surface of head. top of the head between the compound eyes are the three simple eyes, or ocelli (0), arranged in a triangle with the median ocellus in front. Between the lower halves of the large eyes and near the center of the face arise the antenne (Ant), each of which is inserted into a small, circular, membranous socket of the head wall, and consists of a long, basal, 1-segmented stalk carrying a terminal 11-jointed arm movably articulated to the stalk and generally hanging downward from it. (In the drone the terminal arm consists of 12 joints.) The mouth parts are attached at the lower part of the head, and consist of the mandibles (Md) laterally and the maxille (Mx) and labium (Lb) mesially. The latter two include the set of elongate bladelike organs surrounding the protrusible “ tongue,” which to- gether constitute what is commonly known as the proboscis (Prd). 28 THE ANATOMY OF THE HONEY BEE. When not in use the parts of the proboscis are bent back beneath the head. By referring to figure 9B, giving a posterior view of the head, it will be*seen that the basal parts of both the maxille (Sf) and the labium (J/¢) are suspended in a large hollow on the back of the cranium. This may be called the cavity or fossa of the proboscis (PrbFs). Between the mandibles on the front of the head (fig. 9A) is a transverse movable flap, the labrum (Lm), attached to the lower edge of the front wall of the head and constituting the upper hp. The mouth (Mth) lies behind the labrum and the mandibles close beneath it. Below the antennal sockets is a transverse, slightly arched suture (a) which turns downward on each side and extends to the inner angles of the bases of the mandibles. The area bounded by this suture is the clypeus (Clp) and the suture itself may be called the clypeal suture. On the posterior surface of the head (fig. 9B) is seen the pen- tagonal foramen magnum (For) by means of which the cavity of the head communicates with that of the thorax and through which pass the nerves, cesophagus, blood vessel, and tracheal tubes. A small rod (ten) inside the head arches transversely over the fora- men magnum, cutting it into a dorsal and a ventral half. At each side of the foramen is a large pit (¢) which marks the base of an internal chitinous beam of the head known as the mesocephalic pillar. The opposite end of this pillar unites with the front wall of the head on the clypeal suture below the antenne, where it produces another smaller pit (0). Below the foramen magnum and separated from it by a wide trans- verse bridge of the cranial wall is seen the large fossa of the proboscis (fig. 9B, PrbFs) having the shape of an inverted U. The side walls of this cavity are chitinous and from their upper edges are suspended the maxille, while the base of the labium is contained in the mem- branous floor of the fossa. The base of the labium projects from the head beneath or behind the mouth opening and its dorsal surface forms the floor of a preoral cavity surrounded by the bases of the mouth parts and labrum. It will be seen from the above description that the head wall of the bee contains no suture except that bounding the clypeus and the one which separates the labrum from the latter. Many of the ‘higher insects have the head wall completely continuous, showing no division at. all into sclerites, but, in such forms as a grasshopper or cockroach, and, in fact, most of the lower insects, the head as well as the other parts of the body is made up of a number of plates. Hence this may be regarded as the primitive condition, and it is presumed that the head of the bee has been produced from one whose wall was divided by sutures into a number of distinct parts. Therefore the different THE HEAD OF THE BEE AND ITS APPENDAGES. 29 regions of the bee’s head may be named according to the sclerites with which they correspond in other insects. Thus, the part of the face above the clypeus and between the compound eyes may be called the front (fig. 9A, Ft), the parts below the compound eyes the genw (Ge), and the top of the head the vertex (Vz). The area on the back of the head around the foramen magnum may likewise be termed the occipital region (fig. 9B, Oc) and the parts be- hind the gene and the lower halves of the compound eyes the postgene (Pge). The worker, queen, and drone differ conspicuously in the shape and size of the head, as will be seen by comparing A, B, and C of figure 10. In these drawings the front has been removed in order to show various internal parts, which will be described later. While the head of the worker (A) is triangular in facial view, that of the queen (B) is more rounded and wider in proportion to its length. The head of the drone (C) is much larger than that of the female and is nearly cir- cular in outline. In shape the head of the queen is intermediate between that of the worker and that of the drone, but in size it is somewhat smaller than the head of the worker. The eyes (Z’) of the worker and queen are about equal, but those of the drone are enormously. enlarged and are broadly contiguous on the vertex and the upper part of the front. On this account the ocelli (0) of the drone are crowded down on the front nearer the bases of the antenne and the frent Fic. 10.—A, anterior view of head of itself is very much narrowed above. worker, with front, antennm, and Tl : ; Pits proboscis remoyed; B, correspond- ye antenne of the drone consist of ing view of head of queen; C, same 13 segments, while those of the females —°f_ drone. have but 12 segments. The mandibles are largest proportionately in the queen and are very small in the drone. Those of the worker have a smooth terminal edge, while this edge is notehed in the queen and the drone. The parts of the proboscis are much longer in the worker 30 THE ANATOMY OF THE HONEY BEE. and capable of much more action than in the queen and drone, which are almost entirely dependent upon the workers for their food. The internal structure of the cranium may be studied best in a longi- tudinal section of the head (fig. 11). In order to prepare a section for this purpose imbed the head in paraffin and then carefully slice off one side with a sharp knife or razor just outside of the bases of the mandible and antenna. Holding the remainder in the block of paraffin or fastening the whole in a dish of water or alcohol, care- fully dissect away the soft parts from the head cavity so as to expose Fic. 11.—