Are there pheromonal dominance signals in the Bombus hypnorum L (, )? M Ayasse, T Marlovits, J Tengö, T Taghizadeh, W Francke

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M Ayasse, T Marlovits, J Tengö, T Taghizadeh, W Francke. Are there pheromonal dominance signals in the bumblebee Bombus hypnorum L (Hymenoptera, Apidae)?. Apidologie, Springer Verlag, 1995, 26 (3), pp.163-180. ￿hal-00891257￿

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Are there pheromonal dominance signals in the bumblebee Bombus hypnorum L (Hymenoptera, Apidae)?

M Ayasse T Marlovits J Tengö T Taghizadeh W Francke

1 Institute of Zoology, Dept of Evolutionary Biology, Althanstr 14, A-1090 Vienna, Austria; 2 Ecological Research Station of Uppsala University, S-38600 Färjestaden, Sweden; 3 Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg 13, Germany

(Received 1st November 1994; accepted 3 February 1995)

Summary — In the bumblebee Bombus hypnorum (Apidae) 132 chemical compounds could be identified by GC/MS and coinjection. The behavior of individual workers was observed to characterize them as dominant, subordinate or foragers. Queens, dominance groups of workers and newly emerged workers showed significant differences in both the amounts and proportions of volatiles, in the status of the ovaries, in the size of the fat body, and in the body size. bumblebee / Bombus hypnorum / dominance / volatile bouquets / chemical analysis

INTRODUCTION recognition has been demonstrated (Buckle, 1982), and in primitively eusocial Polistes wasps, chemical cues may function to main- In all eusocial Hymenoptera queen control tain dominance hierarchies in over workers is probably inseparable from conjunction with direct the mechanism of queen recognition aggression (West-Eberhard, (Fletcher and Ross, 1985; Keller and 1981). The evolution of specific queen Nonacs, 1993). The recognition / inhibition pheromones might coincide with the devel- system hypothesized for highly eusocial opment of a larger worker population inside Hymenoptera may be derived from a simpler the nest (Velthuis, 1976). In such cases, recognition system of primitively eusocial agonistic behavior by a queen towards all species where each individual is recognized individuals is impossible and the single by a specific composition of the odor com- queen needs to develop a warning or recog- ponents (Michener, 1977). In primitively nition system to extend her influence pres- eusocial halictine bees, pheromonal queen ence beyond the reach of her mandibles and sting. In honey bees, the queen’s In contrast to B terrestris, no evidence pheromone is transmitted within the colony was found in B impatiens for a queen- mainly by retinue workers (Naumann et al, derived pheromonal dominance signal 1991). (Pomeroy, 1981); queens with their , like many other primitively mandibles removed were reported to retain eusocial bees, have 2 castes: queens and their dominant position by physical interac- workers (Michener, 1974). Queens are tions with the workers, which might suggest larger than workers, live longer and mate. that the mechanism or existence of Only the mated queens lay fertilized eggs. pheromonal control may differ from species Therefore, they alone are responsible for to species. In more primitive species with a the production of female offspring. Among relatively small number of workers, a poorly the workers, a division of labor exists. There developed use of pheromones and a greater are foragers, guard bees and nest bees. reliance upon agonistic behavior may lead to a dominance is Furthermore, hierarchy a queen’s dominance. established among them which is partly con- B is presumably a bumblebee nected to the different tasks performed by hypnorum a more state the workers. Some of them show queen- species representing primitive in to B ter- like behavior; they become egg-layers when of social evolution comparison smaller colonies and a the queen loses her dominance at the end of restris, having colonial cycle. Dominant workers show weaker caste polymorphism. Furthermore, aggressive behavior towards other workers similar to honeybees, in B terrestris larvae (van Doom, 1988; Röseler and van Honk, are determined to become workers or 1990). queens during their first 3.5 d, while in B the amount of food a larva The fertility of workers is not only con- hypnorum receives its whole of trolled by the presence or absence of a dom- throughout period influences the caste determi- inant queen but also by other dominant development workers (Röseler and van Honk, 1990). In nation (Röseler, 1970). In a study analyz- Bombus terrestris, the queen retards the ing the Dufour’s gland secretion of B hyp- development of workers’ ovaries by means norum (Hefetz et al, 1993), internidal and of pheromones (van Honk et al, 1980; intranidal variation in the secretions of work- Röseler et al, 1981) and she inhibits ovipo- ers was found. Workers within a nest clus- sition when workers have fully developed tered into defined odor groups according to ovaries (van Honk et al, 1980, 1981). The their glandular composition. In addition, there queen’s inhibitory pheromone is produced in was a correlation between the odor patterns her mandibular glands and spread over her and the size of the bees that might reflect dif- If the body surface (Röseler et al, 1981). ferent dominance groups of workers. foundress queen is lost or experimentally The objectives of our present study were removed, ovaries start to develop and eggs to investigate and compare the odor bou- are produced in one or more of her of and different functional orphaned workers. Whether some workers quets queens retard the ovarian development of others worker groups of B hypnorum, with the and stabilize the dominance hierarchy by intention of evaluating the evolution of caste- pheromonal control (Katayama, 1974; and sub-caste-specific pheromonal recog- Röseler and Röseler, 1977) or by specific nition or dominance signals, which has not dominance behavior is as yet unknown. Fur- yet been studied in bumblebees. Volatiles thermore, no chemical analyses have been from different sources and individual bees performed to identify the queen pheromone. were analyzed by capillary GC and GC/MS. MATERIALS AND METHODS extracted in 0.1 ml pentane (Uvasol, Merck) for 24 h.

Rearing bumblebees Size and reproductive status In May 1993, established colonies of B (Pyrobom- bus) hypnorum (L) were collected from various Prior to dissection, the size of the bees was deter- locations surrounding the Ecological Research mined by measuring the head width and 1 dis- Station of Uppsala University at Öland, SE Swe- tance of the right forewing (distance from the den. Prior to transferring the bees into artificial proximal tip of the discoidal cell to distal tip of the nesting boxes, each female was individually radial cell). The size of the fat body was recorded marked with a number on her scutum. The artifi- as large (1), intermediate (2), small (3), or very cial nesting boxes allowed workers to forage in the small (4) and the status of the ovaries was exam- field. ined. Six ovarian stages were distinguished: 1) ovarioles small, all follicles beyond the vitellogenic phase; 2) vitellogenesis started; 3) vitellogene- sis in a ovarioles Behavioral observations progressive phase; 4) enlarged, no maturated eggs; 5) ovarioles large, with only a few maturated eggs; and 6) ovarioles large, with From mid-June to mid-July 1993, 3 laboratory several maturated eggs (see Michener et al, nests were observed at least 3 times a day under 1971). red light. The interactions between the workers were recorded during periods of 20 min. Seven- teen different behavioral patterns were scored Chemical analysis (see Results). Based on their behavior, 3 different groups (’dominant workers’, ’subordinate work- ers’ and ’foragers’) were distinguished. A Hewlett-Packard 5890 Series II gas chromato- graph, equipped with a DB-5 capillary column (30 m x 0.32 pm) was used, operating at 120°C for 30 followed to 290°C at Sample collection s, by programming 4°C/min (constant flow, 1.6 ml/min). For analy- ses of absolute quantities n-octadecane was Workers belonging to the 3 behavioral groups, added as an internal standard to all samples. plus newly emerged workers (0-2 h old), and GC/MS analyses were carried out with an HP egg-laying queens were collected to obtain 5890 coupled to a VG 70/250 SE. headspace samples. Individuals of the worker groups and queens were killed by freezing and stored at -70°C until dissection. Statistical analysis Individual headspace samples were obtained by placing 1 bee in a glass vial (volume: 30 ml) for 30 min. After careful removal of the bee, the Relative and total amounts of chemical classes of were tested for of dif- vial was stored at -20°C for at least 40 min to compounds significance ferences between and worker condense the odor compounds onto the inner queens groups glass surface. Subsequently, the glass surface with an analysis of variances (Anova) followed a test was rinsed with 3 ml pentane (Merck, Uvasol), by multiple comparison (LSD-test). Single were used for a discrimi- and the sample was concentrated in a capillary compounds stepwise nant function flask to a final volume of 20-40 μl. Cuticular analysis (Backhaus et al, 1987; Norusis, The contribution of each vari- washings were obtained by rinsing an individual 1993a,b). able to the discriminant functions was assessed abdomen for 30 s in pentane (worker: 0.5 ml; its standardized canonical discriminant function queen: 1.0 ml). Heads were cut off from the tho- by coefficient. rax, and the mandibles were gently opened to allow solvent penetration and extracted in 0.2 ml The Spearman rank correlation coefficient pentane for 24 h. Individual Dufour’s glands were was used to test the significance of the female relationships between size of the females, size ordinate workers and foragers in 11 of 17 of their fat bodies, ovarian status and the total behavioral patterns (fig 1). Compared to amounts of volatiles in their extracts. The size of subordinate workers and foragers, domi- the females of different groups was compared nant workers were most in inter- using the unpaired t-test, and the size of the fat aggressive bodies and the status of the ovaries with the actions with other bees. Dominant behavior Mann-Whitney U-test. Computations were per- included bumping and biting but also egg formed using SPSS for Windows (Norusis, laying. Furthermore, dominant workers had 1993a, b). significantly larger ovaries (fig 2) compared to the other worker groups (Mann-Whit- ney, n = 48, p < 0.001) and tended to have RESULTS a large fat body (not significantly different, p > 0.05); 17% showed a large and 60% an intermediate fat body. Subordinate work- Behavioral observations, size ers characteristically walked around within and status reproductive the nest and fed the larvae. Workers’ eggs were recorded in the ovarioles of only one Three worker groups could be identified of the 14 subordinates, while 8 of the 12 based on the tasks they performed and on dominant ones had at least a few to sev- dominance behavior. We observed signifi- eral eggs. The fat body in 7% of the subor- cant differences between dominant, sub- dinate workers was large, and was inter- mediate in 57%. Foragers showed the groups was not significantly different (n = smallest ovaries and a small fat body as 26, p > 0.05). well (0% large, 42% intermediate). Foragers characteristically foraged, warmed the brood, and fed larvae (fig 1). All of the newly Chemical analysis emerged workers had small ovarioles. Inter- estingly, they were similar to the subordi- In Dufour’s gland (DG) and head extracts nate and dominant workers in the size of (HE), cuticular washings (CWS) and the fat body (10% large, 60% intermedi- headspace samples (HS), 132 compounds ate). could be identified by GC/MS analyses and Queens were found to be significantly coinjection (table I). In accordance with larger than workers (t-test, head-width Tengö et al (1991), we found straight chain (HFW): t = 7.21, n = 55, p < 0.001; wing saturated and unsaturated hydrocarbons, length (WL): t = 10.94, n = 55, p < 0.001, branched hydrocarbons, carboxylic acids, fig 3). Within the workers, dominant bees ethyl and methyl esters of fatty acids, unsat- were larger than subordinates (HFW: t= urated and saturated acetates, terpenes and 2.43, n = 26, p < 0.05; WL: t= 2.365, n = 26, terpenoid esters. In all sample types, queens p < 0.05) and foragers (HFW: t = 2.54, n and the worker groups showed striking dif- = 24, p < 0.05; WL: not significant, t= 1.86, ferences in both total amounts (fig 4) and n = 24, p = 0.08). The size of the last 2 relative proportions of volatiles (tables II-V). Qualitative differences between n-Alkanes and alkenes were found to be sample types the major chemical classes of compounds in the Dufour’s glands and in the cuticular With a few exceptions almost no qualitative washings and headspace samples. differences were found between the different sample types. Geranyl citronellol was only Quantitative differences- identified in the cuticular washings, head absolute amounts extracts and headspace samples, but not in the Dufour’s glands. The corresponding The absolute amounts of volatiles were esters hexa- wax-type (geranyl citronellyl found to be highest in breeding queens decenoate and octadecenoate) could be (3-7-fold the amount in comparison to the found in all sample types. While their relative workers, fig 4). Furthermore, they were amounts were below 1% in the Dufour’s higher in dominant than in subordinate work- gland and below 0.5% in the cuticular wash- ers. Smaller amounts of volatiles could be ings and the headspace samples, they rep- detected in foragers, and the smallest in resent the main compounds in the head newly emerged workers. The mean amount extracts, with a relative amount of 20% in of volatile material in the head extracts and workers and more than 30% in queens. the cuticular washings was similar in differ- ent worker groups, but differed from those of unidentified compounds contributed most the queens. In the cuticular washings to the overall discriminant functions; they approximately 270 μg could be identified showed large standardized canonical dis- and about half the amount (130 μg) in the criminant function coefficients in all sample head extracts of queens. The total amount types. Only the headspace samples of dom- of volatiles in the Dufour’s gland was smaller inant and subordinate workers were com- (fig 4). pared with a discriminant analysis (χ2: 19.16, A canonical discriminant analysis signif- DF: 3, p < 0.001, fig 4) because of small icantly separated queens and worker groups sample sizes in queens and foragers. for each sample type for absolute volatile amounts (DG: χ2: 331.38, DF: 52, Quantitative differences- p < 0.0001; HE: χ2: 271.58, DF: 44, p < relative amounts 0.0001; CWS: χ2: 472.73; DF: 72; p < 0.0001). The first discriminant function explained 82% of the variation in the head Whereas dominant and subordinate workers extracts, 79% in the Dufour’s gland and showed very similar patterns of volatiles, almost 100% in the cuticular washings. Ger- they differed from queens, foragers and anyl citronellol (in HE and CWS), alkenes newly emerged workers. The proportions ((Z)-11-pentacosene, (Z)-7-pentacosene), of branched alkanes in Dufour’s gland and branched alkanes (methyl tricosane, methyl head extracts were higher in dominant bees pentacosene), alkadienes (heptacosadiene, than other workers (tables II and III). For- octacosadiene, tricontadiene) and some agers were different from all of the other worker groups in having higher proportions volatile amounts (DG: χ2: 363.03, DF: 24, of unsaturated acetates and alkadienes in p < 0.0001; HE: χ2: 273.42, DF: 52, Dufour’s gland and cuticular washings (table p < 0.0001; CWS: χ2: 272.4, DF: 48, p < IV). The odor bouquets of queens were sig- 0.0001; HS of dominant and subordinate nificantly different from those identified in workers: χ2: 43.58, DF: 6, p < 0.0001, tables the worker bees and were characterized by II-V). More than 90% of the variance was the highest amount of branched alkanes explained by only 1 discriminant function and wax-type esters, while the amounts of for each sample type. Examination of stan- saturated and unsaturated fatty acids were dardized canonical discriminant function small. Dominant workers showed a pattern coefficients again showed branched al- of volatiles similar to queens. kanes, alkenes, alkadienes and geranyl Canonical discriminant analyses suc- citronellol of particular relevance in the sep- cessfully separated queens and worker aration among groups. The power of a dis- groups for each sample type for relative criminant function can also be shown by the

overall percentage of cases classified cor- cues (van Honk et al, 1980; Röseler et al, rectly. For the head extracts, almost 80% 1981). Our behavioral observations sup- of the cases were classified correctly, whilst port the finding of Bollingmo (1989) that a in the Dufour’s gland extracts only 50% were dominance hierarchy is also established classified correctly. While all of the queens among workers in B hypnorum. We could in every sample type were classified cor- classify 3 worker groups: dominant work- rectly, dominant workers were more difficult ers, subordinate workers and foragers, that to classify. Some of them were classified in are characterized also by size and ovariole the group of subordinate workers, suggest- status. Dominant workers often showed ing overlap of the patterns of volatiles of aggressive behavior like bumping and biting dominant and subordinate workers, as can threats towards other workers or even actual be seen in figure 5. biting. Furthermore, they laid eggs. Accord- In all of the sample types, the total ingly, physical interactions seem to be of amount of volatiles was correlated with the major importance in the establishment and dominance head width (Spearman, DG: r = 0.49, maintenance of the hierarchy workers. Observations p < 0.0001, n = 55; HE: r= 0.64, p < 0.0001, among B hypnorum of direct interactions between n = 55; CWS: r = 0.49, p < 0.0001, n = 55) aggressive and with the size of the ovaries (DG: the queen and the workers were rare, how- ever. r = 0.67, p < 0.0001, n = 54; HE: r = 0.59, Possibly, pheromonal queen recogni- tion as a control p < 0.0001, n = 54; CWS: r = 0.67, p < cues, acting queen signal, contribute to the maintenance of her 0.0001, n = 54) but not with the size of the may fat body. In the headspace samples, a sig- dominant position. nificant correlation was detected only A queen or worker pheromonal recogni- between the size of the females and the tion, as hypothesized for primitively euso- size of the ovaries (r = 0.45, p < 0.01, n = cial bees of more populous colonies, should 33). When the queens were excluded from be based on odor, and expressed as varia- the analysis, the total amount of volatiles in tion in patterns of volatile compound com- the CWS was still correlated with the size positions (Hölldobler and Michener, 1980). of the ovarioles (r = 0.58, p < 0.0001, n = Actually, in B hypnorum we found group- 55), but not with the size of the females (r= specific odor bouquets in Dufour’s gland 0.26, p > 0.05, n = 48). and head extracts, cuticular washings, and headspace samples. Recently, caste- and subcaste-specific volatile patterns were also DISCUSSION identified by chemical analyses in the prim- itively eusocial sweat bee Lasioglossum et al, In Bumblebees are good candidates for inves- malachurum, (Ayasse 1991, 1993). tigations of the existence and evolution of both cases, bioassays prove the existence of and dominance queen pheromones and on the occurrence pheromonal recognition remain to be of chemical dominance signals among work- signals performed. ers, because dominance hierarchies have Our knowledge on the glandular origin been found to be based on aggressive and the chemical composition of the queen behavior, chemical cues or both. In the pheromones in social is still in an bumblebee B terrestris, a dominance hier- early stage. Indeed, the honeybee is the archy is established by aggressive interac- only social bee species, for which queen tions at emergence of the first workers (van pheromones have been characterized by Doorn, 1989). The queen dominance is chemical analyses. In the mandibular maintained by the influence of pheromonal glands, a 5-component blend, consisting of 3 acids and 2 aromatic compounds has agers or young workers, possibly indicating been identified (Winston and Slessor, 1992). that dominant workers, besides aggressive In B terrestris, a queen pheromone is sug- interactions, also use a chemical signal to gested to be produced in the mandibular establish and maintain a dominance posi- glands and spread over the body surface tion. (Röseler et al, 1981). Interestingly, in B hyp- In queenless colonies of B terrestris, size norum we found the most striking differ- was found to be the most important correlate ences between the queen and worker of the rank of a worker within the dominance groups in head extracts and cuticular wash- hierarchy (Röseler and van Honk, 1990). In ings, which might indicate the occurrence queenright colonies, the size of a worker is of a queen signal. However, abdominal not as important for becoming an egg-layer glands may also contribute to characterize (van Honk et al, 1981; van Doorn and a queen odor. In honeybees, the mandibu- Hogeweg, 1985; van Doom and Heringa, lar glands are not the only site for production 1986). The activity of the corpora allata and of queen pheromones; tergite glands are ovariole status correlate with rank in B pra- also involved in the secretion (Renner and torum, as dominant bees show the most Baumann, 1964). The results of our dis- developed ovaries (Free, 1955), while there criminant analyses showed the odor bou- was no correlation between the size of a quet of B hypnorum queens to differ more bee and its dominance status. In B hypno- from those of all groups of workers than rum we found dominant workers to be sig- these diverge from each other. Branched nificantly larger in comparison to subordi- alkanes, alkadienes and geranyl citronellol nate ones or foragers. Furthermore, they were of particular relevance in characteriz- had the largest ovaries. Interestingly, we ing queens. Geranyl citronellol was present found a stronger correlation between the in the cuticular washings of the queens but size of the ovaries and the total amount of absent in those of workers. The total amount identified volatiles than between the size of of volatiles in queens was 3-7-fold higher a bee and the total amount of volatiles. than in workers (fig 4). However, the impor- When excluding queens from the statistical tance of qualitative or quantitative differ- analysis, there was no correlation between ences in odor between queens and workers the head width (representing body size) and and their function in signaling pheromonal the volatile amount on the cuticular surface, dominance is presently a matter of specu- while the size of the ovaries was highly cor- lation. related with the amount of detected odor. According to observations of behavior Free (1955) previously suggested that the within B terrestris colonies, "dominant work- scent of an individual bumblebee is possibly associated with the of ers did not have the same dominance signal degree development of its ovaries. as the queens, but they were nevertheless recognizable as highly dominant workers, Our data are in congruence with prevail- probably by some pheromonal support" (van ing hypotheses on the evolution of Doom, 1987). In B pratorum, a dominant pheromonal dominance signals in social worker from a queenless group introduced insects. Hölldobler (1984) suggested that into another queenless group, was recog- in bumblebees "aggressive superiority is nized and attacked by the dominant worker linked to individual discriminators, thus of the latter group (Free, 1955). The pattern enabling nest mates to identify the domi- of volatiles of queens of B hypnorum was nant individual and thereby avoiding costly more similar to that of the dominant workers physical conflicts". The queen would also than to those of subordinate workers, for- profit from avoiding investment of time and energy in repeated conflicts by the use of et identifié 132 composés (tableau I) par a chemical signal. The differences in volatile analyse en CG/MS (chromatographie phase bouquets of queens and workers of B hyp- gazeuse/spectrométrie de masse) et par la norum might constitute the basis for a technique de co-injection. Les reines et les pheromonal recognition signal. Behavioral groupes d’ouvrières ont présenté des diffé- experiments to test the hypothesis of the rences significatives, en fonction de leur existence of pheromonal recognition and comportement et de leur âge, dans la quan- dominance signals in B hypnorum are tité totale de composés volatils et dans leurs presently under investigation. proportions (fig 4, tableaux II-V). Les quan- tités absolues de produits volatils étaient maximales chez les reines et plus élevées ACKNOWLEDGMENTS chez les ouvrières dominantes que chez les subordonnées. De petites quantités ont pu être détectées chez les butineuses et les We wish to thank W Engels, R Paxton and H Paulus for critical reading of the manuscript and quantités les plus faibles ont été trouvées E Zellinger for technical assistance. Grants from chez les ouvrières fraîchement écloses. La the ÖFG and the FWF (Fond zur Förderung der meilleure discrimination des sous-groupes wissenschaftlichen Forschung, P09773-BIO), d’ouvrières a été obtenue par les profils Austria, to M Ayasse and T Marlovits and the volatils des extraits de têtes et des Swedish Natural Science Research Council to J lavages de cuticules. Les ouvrières dominantes et Tengö are gratefully acknowledged. W Francke and T Taghizadeh appreciate funding through subordonnées présentent des profils très the Deutsche Forschungsgemeinschaft. proches l’un de l’autre mais nettement dif- férents de ceux des reines, des butineuses et des ouvrières fraîchement écloses. Les Résumé - Existe-t-il chez le bourdon proportions relatives des alkanes ramifiés Bombus hypnorum L (Hymenoptera, Api- dans les extraits de glandes de Dufour et dae) des signaux phéromonaux de domi- de têtes sont plus élevées chez les abeilles nance ? Nous avons identifié et comparé dominantes que chez les autres ouvrières. les bouquets odorants de reines, de divers Les butineuses se différencient de tous les groupes de dominance d’ouvrières et autres groupes d’ouvrières par des propor- d’ouvrières fraîchement écloses de Bom- tions plus fortes d’acétates insaturés et bus hypnorum. Dans un premier temps le d’alkadiènes dans les extraits de glandes comportement individuel des ouvrières de de Dufour et dans les lavages de cuticules. bourdons a été observé, ce qui a permis de Les bouquets odorants des reines se carac- les classer en dominantes, subordonnées térisent par la proportion la plus élevée et butineuses. Par rapport aux ouvrières d’alkanes ramifiés, d’alcools terpéniques et subordonnées et aux butineuses, les d’esters de cire et diffèrent significativement ouvrières dominantes se sont montrées plus de ceux des ouvrières. Les ouvrières domi- agressives dans leurs interactions avec les nantes présentent un profil volatil semblable autres ouvrières (fig 1). Elles avaient des à celui des reines (fig 5). La discussion porte ovaires significativement plus gros (fig 2) et sur la signification biologique de ces résul- une tendance à avoir un corps gras déve- tats en relation avec l’hypothèse actuelle loppé ; en revanche les butineuses avaient de l’évolution des signaux phéromonaux de les plus petits ovaires et un corps gras peu dominance chez les insectes sociaux. développé. On a réalisé des extraits de glandes de Dufour (DG), des extraits de Bombus hypnorum / dominance / com- têtes (HE), des lavages de cuticules (CWS) posé volatil / bouquet phéromonal / com- et des échantillons de phase vapeur (HS) position chimique Zusammenfassung — Gibt es pheromo- von dominanten Arbeiterinnen waren die nale Dominanzsignale bei der Hummelart Anteile an verzweigten Alkanen größer als Bombus hypnorum L (Hymenoptera, Api- bei allen anderen Arbeiterinnen. Sammle- dae)? Bei der Hummelart Bombus hyp- rinnen zeichneten sich durch höhere Anteile norum wurden die Duftmuster von Köni- an ungesättigten Acetaten und Alkadienen ginnen, verschiedenen Arbeiterinnen- in den Dufourdrüsensekreten und den Vola- Dominanzgruppen und frisch geschlüpften tilen auf der Kutikulaoberfläche aus. Die Arbeiterinnen identifiziert und verglichen. In Volatilbouquets von Königinnen waren durch einem ersten Schritt wurden in Labornes- höhere Anteile an verzweigten Alkanen und tern die Interaktionen von einzelnen Arbei- Wachsestern signifikant verschieden von terinnen 3 mal täglich während Zeiträumen denen der Arbeiterinnen. Von allen Arbei- von je 20 min beobachtet. Anhand der dabei terinnengruppen waren die Duftstoffmuster registrierten Verhaltensmuster konnten 3 von dominanten Bienen denen der Köni- unterschiedliche Arbeiterinnen-Dominanz- ginnen am ähnlichsten. Die biologische gruppen identifiziert werden. Dominante Bedeutung der Ergebnisse wurden anhand Bienen zeigten bei Begegnungen mit sub- der momentan aktuellen Hypothesen zur ordinaten Arbeiterinnen oder Sammlerin- Evolution von pheromonalen Dominanz- nen aggressives Verhalten wie Beißen und signalen bei sozialen Insekten diskutiert. Stoßen mit dem Kopf. Außerdem zeichneten sie sich durch größere Ovarien und einen Bombus hypnorum /Dominanz / Volatil- großen Fettkörper aus. Sammlerinnen hin- bouquet / chemische Zusammensetzung gegen hatten die kleinsten Ovarien und einen kleinen Fettkörper. In Dufourdrüsen-, Kopf- und Kutikulaoberflächenextrakten REFERENCES sowie Headspaceproben konnten mittels GC/MS Koppelung und Koinjektionen 132 Ayasse M, Lübke G, Francke W (1991) Alters- und kas- Substanzen identifiziert werden. Königin- tenspezifische Duftstoffmuster bei der Fortpflanzung malachurum nen und durch unterschiedliche Verhal- der Furchenbiene Lasioglossum (Hymenoptera: Halictidae). Verh Dtsch Zool Ges84, tensmuster und Alter charakterisierte Arbei- 386-387 terinnengruppen zeigten signifikante Ayasse M, Engels W, Hefetz A, Tengö JW, Lübke G, Unterschiede in den relativen und absoluten Francke W (1993) Ontogenetic patterns of volatiles Anteilen einzelner Volatile. Die Gesamt- identified in Dufour’s gland extracts from queens and workers of the primitively eusocial halictine bee, menge an Duftstoffen war bei Königinnen Lasioglossum malachurum (Hymenoptera: Halicti- am größten und bei dominanten Arbeiterin- dae). Insectes Soc 40, 1-18 nen Kleinere größer als bei subordinaten. Backhaus K, Erichson B, Plinke W, Schuchard-Fischer Substanzmengen fanden wir bei Sammle- C, Weiber R (1987) Multivariate Analysemethoden. rinnen und die kleinsten bei frisch geschlüpf- Springer Verlag, New York, USA ten Arbeiterinnen. Innerhalb der Arbeiterin- Bollingmo T (1989) Worker-queen conflict and fitness sich die deutlichsten consequences in a colony of Bombus hypnorum L nengruppen ergaben (Hymenoptera). Fauna Norv Ser B 36, 69-73 Unterschiede der Duftbouquets bei den Buckle GR (1982) Differentation of queens and nest- der Kopfextrakten und den Kutikula aufge- mate interactions in newly established colonies of lagerten Volatilen. Dominante und subordi- Lasioglossum zephyrum. Sociobiology 7, 8-20 nate Arbeiterinnen zeigten ähnliche Duft- Doom A van (1987) Investigations into the regulation of stoffmuster, während Königinnen, dominance behaviour and of the division of labour in Sammlerinnen und frisch Arbei- bumblebee colonies (Bombus terrestris). Neth J Zool geschlüpfte 37, 255-276 terinnen durch davon verschiedene Volatil- Doom A van (1988) Reproductive dominance in bum- charakterisiert werden konnten. bouquets blebees: an etho-physiological study. Thesis, Univ In den Kopf- und Dufourdrüsenextrakten Utrecht, The Netherlands Doorn A van (1989) Factors influencing dominance Michener CD, Brothers DJ, Kamm DR (1971) Interactions behaviour in queenless bumblebee workers (Bombus in colonies of primitively social bees: Artificial colonies terrestris). Physiol Entomol14, 211-221 of Lasioglossum zephyrum. Proc Natl Aca Sci USA 68, 1241-1245 Doom A van, Hogeweg P (1985) Die Entwicklung des agonistischen Verhaltens innerhalb der Arbeiterin- Naumann K, Winston ML, Slessor KN, Prestwich GD, nenkaste und zwischen Arbeiterinnen und der Köni- Webster FX (1991) Production and transmission gin während der Volksentwicklung bei der Erdhum- of honey bee queen (Apis mellifera L) mandibular mel, Bombus terrestris. Mitt Dtsch Ges Allg Angew gland pheromone. Behav Ecol Sociobiol 29, 321- Entomol 4, 328-330 332 Doom A van, Heringa J (1986) The ontogeny of a domi- Norusis MJ (1993a) SPSS for Windows: Base Sys- nance hierarchy in colonies of the bumblebee Bom- tem User’s Guide, Release 6.0. SPSS Inc, Chicago, bus terrestris (Hymenoptera, Apidae). Insectes Soc USA 33, 3-25 Norusis MJ (1993b) SPSS for Windows: Professio- Fletcher DCJ, Ross KG (1985) Regulation of reproduc- nal Statistics, Release 6.0. SPSS Inc, Chicago, tion in eusocial hymenoptera. Annu Rev Entomol USA 30, 319-43 Pomeroy N (1981) Reproductive dominance interac- Free JB (1955) The behaviour of egg-laying workers of tions and colony development in bumble bees (Bom- bumblebee colonies. Br J Anim Behav 3, 147-153 bus Latreille, Hymenoptera, Apidae). Thesis, Univ Hefetz A, Tengö J, Lübke G, Francke W (1993) Inter- Toronto, Canada colonial and intra-colonial variation in Dufour’s gland Renner M, Baumann M (1964) Über Komplexe von sube- secretion in bumble bee species Bombus hypnorum pidermalen Drüsenzellen (Duftdrüsen) der Bie- (Hymenoptera: Apidae). In: Arthropode Sensory Sys- nenkönigin. Naturwissenschaften 51, 68-69 tems. Advances in Life Sciences S (K Wiese, Röseler PF (1970) Unterschiede in der Kastendetermi- G Birkhäuser Kapitsky, Renninger, eds), Verlag, nation zwischen den Hummelarten Bombus hypno- Basel, Switzerland rum und Bombus terrestris. Z Naturforsch 25b, 543- Hölldobler B (1984) Evolution of communication. 548 In: Insect Communication Academic (T Lewis, ed), Röseler PF, Röseler I (1977) Dominance in bumble- 349-377 Press, London, UK, bees. Proc 8th Int IUSSI Congr, Pudoc, Wagenin- Hölldobler B, Michener CD (1980) Mechanisms of iden- gen, The Netherlands, 232-235 tification and discrimination in social In: hymenoptera. Röseler PF, Honk CGJ van (1990) Castes and Repro- Evolution of Social Behaviour: Hypotheses and Empi- duction in Bumblebees. In: Social Insects. An Evo- rical Tests Markl, Chemie GmbH, (H ed), Verlag lutionary Approach to Castes and Reproduction (W Weinheim, Germany Engels, ed), Springer Verlag, Berlin, Germany, 147- Honk CGJ van, Velthuis HHW, Röseler PF, Malotaux 166 ME The mandibular of Bombus ter- (1980) glands Röseler PF, Röseler I, Honk CGJ van (1981) Evidence restris queens as a source of queen pheromones. for inhibition of corpora allata activity in workers of Entomol Exp Appl 28, 191-198 Bombus terrestris by a pheromone from the Honk CGJ van, Velthuis HHW, Hoogeveen JC (1981) queens’s mandibular glands. Experientia 37, 348- Factors influenzing the egg-laying of worker in a cap- 351 tive Bombus terrestris Behav Ecol Sociobiol colony. Tengö J, Hefetz A, Bertsch A,Schmitt U, Lübke G, 9, 9-14 Francke W (1991) Species specifity and complexity Katayama E (1974) Egg-laying habits and brood-deve- of Dufour’s gland secretion of bumble bees. Comp lopment in Bombus hypocrita (Hymenoptera, Api- Biochem Physiol 99B, 641-646 1. habits of and workers. dae). Egg-laying queens Velthuis HHW (1976) Egg laying, aggression and domi- Kontyu 42, 416-438 nance in bees. Proc XV Int Congr Entomol, Washing- Keller L, Nonacs P (1993) The role of queen phero- ton, USA, 436-449 mones in social insects: control or queen queen West-Eberhard MJ (1981) Intragroup selection and the Anim 787-794 signal? Behav 45, evolution of insect societies. In: Natural Selection Michener CD (1974) The Social Behaviour of the Bees, and Social Behavior (RD Alexander, DW Tinkle, Harvard University Press, Cambridge, MA, USA eds), Chiron Press, New York, USA Michener CD (1977) Aspects of the evolution of castes Winston ML, Slessor KN (1992) The essence of in primitively social insects. Proc Int Congr IUSSI, royalty: honey bee queen pheromone. Am Sci 80, Wageningen, The Netherlands, 8, 2-6 374-385