Gunther Lübke

Tarsal secretion marks food sources in bumblebees (Hymenoptera: Apidae)

SummaryScent-marking of artificial food sources by workers of the bumblebee,Bombus terrestris, was investigated. Odour marks deposited on artificial flowers were subsequently collected and chemically analysed. Alkanes and alkenes were identified as the main components. The behaviour mediating capacity of synthetic mixtures of the identified compounds was bioassayed using an artificial flower system. A mixture of alkanes and alkenes, close to natural proportions, released regular foraging behaviour. The reaction proved to be dose-dependent.

Robber bees (Lestrimelitta limao) and their host chemical and visual cues in nest defense byTrigona (Tetragonisca) angustula (Apidae: Meliponinae)

The nest of the stingless bee,Trigona (Tetragonisca) angustula, is guarded by bees positioned in the nest entrance and others hovering in front of it. Hovering guard bees track returning foragers sideways along the last 10 cm in front of the nest, but intercept and incapacitate nest intruders by clinging with mandibles to wings and legs. When attacked by the cleptobiotic stingless beeLestrimelitta limao, the colony strengthens its aerial defense with hundreds of additional hoverers. To test our hypothesis that this reaction is due to interspecific chemical communication based on kairomone effects, we presented synthetic cephalic volatiles of both species at the nest entrance and counted the number of bees leaving the nest and taking up hovering positions. We conclude that guard bees recognizeL. limao by the major terpenoids of their volatile cephalic secretions, geranial, neral (=citral) and 6-methyl-5-hepten-2-one; other components may fine-tune this recognition. The effect of chemical stimuli is not significantly enhanced by combination with a dummy ofL. limao. Guard bees, we hypothesize, respond to this kairomone by secreting a species specific alarm pheromone; a major component of this pheromone, benzaldehyde, recruits additional bees to defend the nest.

Identification of oxygen containing volatiles in cephalic secretions of workers of Brazilian stingless bees

Os constituintes volateis das secrecoes cefalicas de 11 especies brasileiras de abelhas sem ferrao da linha Tetragonisca - Tetragona foram analisados. Foram identificados 145 compostos, por cromatografia gasosa e espectrometria de massas, dentre os quais 72 esteres, 22 alcoois, 16 acidos carboxilicos, 13 terpenos, 8 aldeidos, 4 compostos aromaticos, 2 lactonas e 1 diidropirano. As relacoes estruturais, origem e a distribuicao detes compostos sao discutidas. Com respeito a composicao qualitativa e quantitativa, cada especie mostra um buque de odores, os quais sao obtidos a partir de componentes poucos especificos. Em algumas especies proximamente relacionadas foram observadas similaridades no buque de odores. As fragmentacoes no espectro de massas de esteres graxos e dos esteres insaturados derivatizados com DMDS sao discutidas em detalhes.

Mandibular Gland Volatiles and Their Ontogenetic Patterns in Queen Honey Bees, Apis mellifera carnica.

Extracts of mandibular glands taken from adult queens of the honey bee, Apis mellifera carnica, were analysed by gas chromatography-mass spectroscopy. More than 100 compounds could be identified among which oxygenated fatty acids with six, eight, 10 and 12 carbon atoms are particularly interesting since they show structural relationships to the queen substance, (E)-9-oxo-2-decenoic acid. Changes in the patterns of volatiles were followed up from emergence until the full dominant status of an egg-laying queen in a strong colony. Generally, the amount of volatiles per gland was found to increase with age. The final level of queen substance (9-ODA) content is reached at the postmating stage about 10 days after emergence. Ontogenetic patterns of concentrations were determined for those components regarded to predominantly contribute to the royal pheromone. Characteristic compositions of signals, possibly involved in the premating, mating and postmating dominance status of a honey bee queen are discussed. Copyright 1997 Elsevier Science Ltd. All rights reserved

Species specificity and complexity of Dufour's gland secretion of bumble bees

1. 1. Dufours gland secretions of nine westpalaearctic bumble bee species, representing Terrestribombus, Pyrobombus and Megabombus, were analysed by gas chromatography and mass spectrometry. 2. 2. The secretions were dominated by uneven numbered straight chain alkanes from heneicosane to hentriacontane, each alkane accompanied by up to 10 positional alkene isomers. 3. 3. Various esters dominate among the 64 oxygen-containing compounds found. 4. 4. This is the first report on Dufours gland secretion of bumble bees. The secretion is species specific. Subgeneric and tribe specific patterns are indicated. 5. 5. Characteristics for species separation of workers of the Terrestribombus group are presented. 6. 6. The possible communicative function of the secretion is discussed.

Host-parasite relationships in six species ofSphecodes bees and their halictid hosts: Nest intrusion, intranidal behavior, and Dufour's gland volatiles (Hymenoptera: Halictidae)

Nest invasion behavior was studied in six kleptoparasiticSphecodes species at four nesting sites of their respective social and solitary hosts.Sphecodes females preferred to enter unguarded nests. Nest intruding strategies observed in the differentSphecodes species did not depend on whether host species were solitary or social, as long as the nesting cycle of a social host was in the solitary stage (i.e., a single host female). Observation of intranidal behavior revealed thatSphecodes monilicornis females kill all host individuals within an usurped nest. They stay in the nest for several hours, laying eggs in adequately provisioned brood cells. Gas chromatography-mass spectrometry analyses of Dufours gland secretions revealed species-specific compositions. Qualitative comparisons of whole patterns and quantitative comparisons considering the predominant hydrocarbons common to both host and parasite contradict the hypothesis of chemical mimetism, a mechanism supposed to permit parasite intrusion by qualitatively similar odor bouquets in host and parasite females.

Ontogenetic patterns of volatiles identified in Dufour's gland extracts from queens and workers of the primitively eusocial halictine bee,Lasioglossum malachmum (Hymenoptera: Halictidae)

SummaryOntogenetic patterns of volatile compounds identified in Dufours gland extracts from queens and workers of the primitively eusocial sweat beeLasioglossum malachurum (K.) were compared. Only young unmated queens showed high proportions of isopentenyl esters, while macrocyclic lactones were dominant in old breeding queens, spring queens, and workers. In young queens the relative and absolute amounts of volatiles changed one day after mating. A discriminant analysis revealed significant differences in odor patterns of unmated and mated young queens. The fat body was the largest in young females, while eggs could be recorded only in breeding queens. Possible functions of different odor components in the investigated female groups are discussed.

Ontogenetic patterns in amounts and proportions of Dufour's gland volatile secretions in virgin and nesting queens of Lasioglossum malachurum (Hymenoptera: Halictidae).

Abstract In the primitively eusocial sweat bee, Lasioglossum malachurum, 66 volatile compounds could be identified from queen Dufour’s gland secretions. The patterns found in gynes and in old nesting queens differed in the absolute amounts of extractable volatiles as well as in the relative proportions. 3-Methyl-3-butenyl octadecanoate is the main component in gynes, while 18-octadecanolide, 20-eicosanolide and 22-docosanolide largely dominate the bouquets of old queens. The probable roles of some specific compounds in pheromonal communication of mates and in nest recognition are discussed. Correlations with the volume of the fat body and the vitellogenic status of the ovary are described.

Species specificity of Dufour's gland morphology and volatile secretions in kleptoparasitic Sphecodes bees (Hymenoptera: Halictidae)

In seven parasitic Sphecodes species, the specificity of Dufours gland morphology and volatile secretions was studied. As compared to nesting halictid species, the gland is reduced in size. Its morphology is ribbon shaped and unilobed or bilobed. GC-MS analyses of gland extracts revealed hydrocarbons and long-chain fatty acid esters to be the predominant compounds. Altogether, 54 components were identified, each species being characterized by a specific qualitative odour pattern. Lactones, typically found in ground-nesting halictids, are absent in Sphecodes. Comparing the occurrence of the volatile components by using a Wagner-network procedure resulted in an arrangement of the species corresponding to the classification according to the gland morphology. The Sphecodes showing n-pentacosane as the major compound also share the bilobed gland morphology. Possible functions of Dufours gland secretions in Sphecodes bees are discussed.

Dose-dependent inhibition of emergency queen rearing by synthetic 9-ODA in the honey bee, Apis mellifera carnica

In the honey bee colony queen rearing is usually suppressed by releaser effects of the queens pheromone. This is part of the dominance hierarchy maintaining the monogynous homeostasis. Under queenless conditions, the queens control over the construction of emergency queen cells by the workers can be substitued by exposure to only one component of the mandibular pheromone secretion of a queen, the main compound (E)-9-oxo-2-decenoic acid. A novel and simple synthesis of (E)-9-oxo-2-decenoic acid is described, and a bioassay was developed by which a dose-dependent effect of synthetic (E)-9-oxo-2-decenoic acid presented on a dummy bee was evaluated.