IS THE ORIENTATION OF CELLS IN THE NATURAL HONEY BEE COMB, CHOSEN BY BEES, RANDOM?

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1 Vol. 50 No Journal of Apicultural Science 33 IS THE ORIENTATION OF CELLS IN THE NATURAL HONEY BEE COMB, CHOSEN BY BEES, RANDOM? Irina Shumakova 1, Alexander Komissar 2 1Schmalhausen Institute of Zoology, Kiev, Ukraine, plazmist@i.com.ua 2National Agricultural University, Kiev, Ukraine. alex-kom@nucs.kiev.ua Received 27 April 2006; accepted 06 November 2006 S u m m a r y The orientation of cells in the natural honey bee combs attached to the horizontal and sloped surfaces was investigated. 263 samples of newly constructed natural combs were obtained. The orientation of cells was measured with 1 accuracy and every comb was classified as having horizontal, vertical or intermediate type of cell orientation. No statistical difference was found in the occurrence of three orientation modes for combs with bee cells. A small (10 20%) advantage of vertical orientation in the combs with drone cells was observed. The distribution of cell orientation modes in the naturally-built combs was independent of cell orientation in the neighbouring combs. Most of the combs attached to sloped bars had an intermediate orientation of cells, but an evaluation of their orientation according to the top bar demonstrated that the majority of combs had a vertical orientation with rows of cells parallel to the sloped bar. The regular cell pattern appeared to depend on the starting position on the top bar, not on gravity. The orientation of cells in the combs depends on the orientation of the first cell, built by bees. Keywords: Apis mellifera, comb construction, cell orientation. INTRODUCTION According to three pairs of parallel walls, the hexagonal cells of honey bee comb form a regular pattern of three diagonal rows set at 60 to each other. In vertical combs, the orientation of cell rows with one pair of parallel horizontal or vertical walls has been called horizontal or vertical cell orientation (Wedmore 1929). In the combs from skeps, these two orientations were equally frequent, with intermediate orientations seldom occurring (Thompson 1930). Beeswax sheets with cell bases of only vertical orientation have been used for over a century as a foundation for comb building in movable frame hives and this orientation was even called right way in contrast to wrong way horizontal orientation. But in special experiments, the foundation cell orientation was found not to be important for its acceptability for comb construction (Hepburn 1983). Although the orientation of comb cells is evidently not of vital importance for honeybees, the question still remains as to why they choose one or another orientation in every peculiar case. MATERIALS AND METHODS Natural combs were built in 12 honey bee colonies (Apis mellifera L.), which were kept in Langstroth and Ukrainian hives over the period of two summers (2001 and 2002). In contrast to the Langstroth hives, the frames in the Ukrainian hives are taller-than-broad. The wax foundation is rotated 90 in the Ukrainian frame and the orientation of cells is horizontal. The hives were adjusted to the horizontal level with the help of a level gauge. The top bars of empty frames were used as the attachment sites for comb building. Additional bars were fixed in parallel or at the tilting angle 15±2 to the top bar in the

2 34 taller-than-broad frames (300 x 430 mm) of Ukrainian hives. Small frames (75 x x 150 mm) from 30 mating micronucleus hives were also used (Fig. 1). In the majority of cases, the bees built combs with drone cells and only in the second half of July did part of the combs consist of worker bee cells. The mating babynucs were used for quick building of combs with bee cells. All colonies and babynucs were queenright and received additional feeding with sugar syrup. Frames were examined daily and samples of the early stages of comb building on the top bar were obtained. The orientation of cells in all combs was measured with 1 accuracy. The precise horizontally or vertically orientated cells are constructed only in the combs with artificial foundations, as wild combs always have deviations from straight lines. Combs with a deviation of cell rows ±10 from horizontal or vertical line were referred to as vertical or horizontal orientation, accordingly (Fig. 2). The orientation of the hexagonal cells changes to its opposite after a 30 turn. The combs with cells within the intermediate range were defined as combs with intermediate or oblique orientation of cells. The influence of the first built cell on the orientation of cells in the comb, constructed later on, was examined in the following experiment. A piece of wax foundation with only one cell base, orientated horizontally or vertically, was attached to the lower surface of the top bar of the babynuc frame (Fig. 3) and it was introduced to the bees, having a need of free combs, as starting a cell for comb construction. The distance between the top bar and the cell base corresponded to the dimensions of the attachment cell, as it takes place in the natural comb (Shumakova and Komissar 2005). Altogether, 263 natural combs were built, of which 107 were with drone cells and 55 with worker cells attached to a horizontal surface, 29 combs with drone cells and 36 with worker ones attached to the sloped bars, 32 combs were built from the starting cell. The statistical evaluations were made according to Urbah (1963). RESULTS AND DISCUSSION The results of measurements of cell orientation in the combs from Ukrainian and Langstroth hives with drone cells and from babynucs with worker cells are shown in the Table 1. After comparison of parts, affecting every orientation type, using Fisher s ϕ-corner criterion, no statistical difference in occurrence of three orientation modes for combs with bee cells was revealed. Only a small (45% to 27 28%) advantage of vertical orientation in the combs with drone cells was observed. (Table 1). Combs with bee and drone cells were built in colonies of different size: drone cells in commercial colonies and bee cells in the mating babynucs, but it was assumed that building behavior and, especially, the orientation of combs were not dependent on colony size. These results do not support the observations of Thompson (1930), where only 5% of combs from sceps had an intermediate orientation of cells, and the conclusion of Hepburn (1986) about the rear occurrence of a tilted cell pattern in comparison to vertical and horizontal modes in feral honeybee nests. This difference may possibly be explained by the different methods of ascription of definite comb to definite cell orientation pattern. The orientation of cells in the combs, built on a beeswax foundation in Ukrainian hives is horizontal and in Langstroth ones it is vertical. Frames without foundations for natural comb construction were placed into hives of both types between frames with cells of appropriate orientation. The resulting distribution of cell orientation modes in the naturally-built combs showed no differ-

3 Vol. 50 No Journal of Apicultural Science 35 Fig. 1. Samples of natural combs from mating baby nucs with vertical, intermediate and horizontal (from left to right) orientation of cells. Fig. 2. Evaluation of cells orientation in natural honey bee combs. Left: vertical orientation; right - horizontal one. In all cases, where orientation of the rows of cells had more than a 10 shift from vertical or horizontal line, it was regarded as intermediate. ence between Ukrainian and Langstroth hives (Table 1). The influence of neighbouring cell pattern as a reference cue was not observed in this experiment despite the fact that the bees-builders were bred in combs with different cell patterns. The experiments of Oelsen and Rademacher (1979) with newly emerged bees also rejected the possible influence of the cell pattern, in which bees were reared on their subsequent proclivities as to cell orientation. When bees were provided with only narrow wax strips of some pattern, they constructed combs according to the pattern given, independent of the type from which they were reared. Thus, information about the cell pattern of the mother comb and of the neighbouring, already-constructed combs (which was not located immediately at the time and site of building) was evidently of no importance for bees. The experiments with the sole starting cell (Table 2) also showed a strong tendency to follow the proposed type of cell pattern in the comb construction. At the beginning of work, this cell was rebuilt by bees and made almost round. It was impossible to evaluate its orientation at that mo-

4 36 Fig. 3. The pieces of artificial wax foundation with one cell base, having vertical (left) or horizontal (right) orientation were proposed to bees for the further building. Table 1 Orientation of cells in the natural honey bee combs. V vertical, I intermediate and H horizontal orientation, N, n number of combs. Type of cells Drone Worker Hive Orientation of cells in movable frames Ukrainian Horizontal 27 Langstroth Vertical 80 Drone cells together 107 Mating babynucs Not taken into account N Orientation of cells V I H n % n % n % 45* 28* 27* n % No significant difference in every type of cell orientation between two types of hives * Difference between vertical and other orientations is significant P> Difference between every pair of orientations is not significant ment. Nevertheless, the original orientation of this cell in the majority of cases defined the orientation of cells in the future comb. Most of the combs attached to sloped bars had an intermediate orientation of cells (Table 3), but evaluation of their orientation according to the top bar demonstrated that the majority of combs had a vertical orientation. The combs side edges deviated from the perpendicular to the bar at the angle of bar inclination, but the regular cell pattern did not demonstrate features of incline compensation. It appeared to depend on the starting position on the top bar, not on gravity. Pratt (2000) also derived the orientation of cells within the comb from substrate orientation. After the new nest cavity is occupied, the honey bee swarm solves the problem of orientation of the set of parallel combs inside it through some process (about which little is known) and maintains the direction of combs orientation in the parent colony (De Jong 1982). Are there any factors determining the orientation of hexagons during the building of the comb? In the wild nests of honey bees, both types of comb orientation can be found in a single nest (Taber and Owens 1970). Combs built from two or several independent starting

5 Vol. 50 No Journal of Apicultural Science 37 Table 2 Orientation of worker cells in the natural honey bee combs from the mating babynucs, constructed with or without starting cell. Cell orientation Control Without start cell, (N= 55) Experiment 1 Horizontal start cell, (N=20 ) Experiment 2 Vertical start cell, (N= 16 ) N % N % N % Vertical * 8 50* Intermediate Horizontal * 3 19* + Difference between every pair of orientations is not significant * Difference between two experiments is significant P>0.95 Table 3 Orientation of worker and drone cells in the combs, attached to the sloped (15±2 ) top bars according horizon and according the bar. V, I and H vertical, intermediate and horizontal orientation; V = rows of cells are parallel to the bar (±10 ), H perpendicular to the bar (±10 ) and I - have intermediate orientation according to the sloped bar. Kind of cells Worker cells 36 Drone cells 29 Together 65 N Orientation of cells (n and %) According horizon According top bar V I H V I H n % * 25* 14* n % * 17* 17* n % 26** 46** 28** 63* 22* 15* * Difference between vertical and other orientations is significant Ð>0.95 ** Number of combs with intermediate orientation prevails significantly (Ð>0.95) sites on the same top bar were also observed. Parts of the resulting comb had a different cell orientation. CONCLUSIONS 1 Vertical, horizontal and intermediate (oblique) orientation of cells in natural honey bee combs, attached to horizontal surfaces, occurred with almost the same frequency with a small advantage of vertical orientation in the combs with drone cells. 2 The rows of cells in the natural combs, attached to sloped bars, in the majority of cases (more than 60%) were orientated parallel to the bar, in contrast to the combs attached to the horizontal surfaces. 3 The distribution of cell orientation modes in the naturally built combs was independent of cell orientation in the neighbouring combs and in the mother combs of bee-builders. 4 The dependence of the orientation of cells in the natural comb from the orientation of a single cell, offered to bees as a model, was statistically sig-

6 38 nificant. Thus, it is possible to conclude that the orientation of cells in the combs depends on the orientation of the first cell built by bees. REFERENCES De Jong D. (1982) Orientation of comb building by honeybees. J. Comp. Physiol., 147: Hepburn H.R. (1983) Comb construction by the African honeybee, Apis mellifera adansonii. J. Ent. Soc. Sth. Afr., 46,1: Hepburn H.R. (1986) Honeybees and Wax, Springer-Verlag, 205 pp. Oelsen G. Von, Rademacher E. (1979) Untersuchungen zum Bauverhalten der Honigbiene (Apis mellifica). Apidologie. 10: Pratt S.C. (2000) Gravity-independent orientation of honeycomb cells. Naturwissenschaften, 87: Shumakova I., Komissar A. (2005) Classification of incorrect cells in honeybee combs. XLII Naukowa Konferencja Pszczelarska, Pu³awy, Materia³y z Konferencji, P Taber S., Owens C.D. (1970) Colony founding and initial nest design of honey bees, Apis mellifera L. Anim. Behav., 18: Thompson F. (1930) Observations on the position of the hexagons in natural comb building. Bee World. 11: 10.7 Urbah V.U. (1963) Matematicheskaia statistika dlia biologov i medikov [Mathematical statistics for biologists and physicians], Izd. AN SSSR, 323 s. (in Russian) Wedmore E.B. (1929) The building of honey comb. Bee World. 10: CZY ORIENTACJA KOMÓREK W NATURALNYM PLASTRZE MIODU JEST PRZYPADKOWA? Shumakova I., Komissar A. S t r e s z c z e n i e W pracy zbadano orientacjê komórek naturalnych plastrów miodu, przyczepionych do powierzchni poziomych i pochy³ych. Otrzymano 263 próbek nowo skonstruowanych plastrów miodu. Orientacja komórek zosta³a zmierzona z dok³adnoœci¹ do 1, a ka dy plaster zosta³ sklasyfikowany jako posiadaj¹cy poziom¹, pionow¹ lub poœredni¹ orientacjê komórek. Nie wykryto statystycznej ró nicy w wystêpowaniu trzech typów orientacji w komórkach plastrów. Zaobserwowano niewielk¹ (10 20%) przewagê orientacji pionowej w plastrach z komórkami trutni. Dystrybucja typów orientacji komórek w naturalnie zbudowanych plastrach nie by³a zale na od u³o enia komórek w s¹siednich plastrach. Wiêkszoœæ plastrów przyczepionych do pochy³ych beleczek charakteryzowa³a poœrednia orientacja komórek, ale ocena ich wzglêdem górnej beleczki wykaza³a, e wiêkszoœæ plastrów posiada³a orientacjê pionow¹, w której rzêdy komórek by³y u³o one równolegle do beleczki pochy³ej. Mo na wyci¹gn¹æ wniosek, e regularny wzorzec komórek zale y od pozycji pocz¹tkowej na górnej beleczce, a nie od grawitacji. Orientacja komórek w plastrach zale y od orientacji pierwszej komórki zbudowanej przez pszczo³y. S³owa kluczowe: Apis mellifera, konstrukcja plastra miodu, orientacja komórek.