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Females of the solitary digger wasp tribe Philanthini , called the beewolves (Hymenoptera, Crabronidae), cultivate strains of symbiotic bacteria that belong to the genus Streptomyces in unique and highly specialized glands in their antennae. The glands consist of large reservoirs that are surrounded by numerous gland cell complexes (class III). The symbionts are cultivated inside the reservoirs and are probably provisioned with nutrients secreted from the surrounding glands and/or sequestered from the hemolymph. The wasp female delivers the bacteria into the subterranean brood cell prior to oviposition. Fully grown larvae take up the bacteria and apply them to their cocoon. There the bacteria produce several antibiotics that protect the wasp offspring against fungus infestation. Hitherto Streptomyces bacteria were detected in the antennae of 38 species of the Philanthini. However, a detailed morphological analysis of the antennal glands is only available for a few species. In order to shed light on the evolutionary history of the association between beewolf wasps and bacteria, we investigated the morphology of the antennal glands of another 14 Philanthus species from the Palearctic, Paleotropic, and Nearctic. We generated 3D-models of the glands based on serial semithin sections and/or micro-CT (μCT). Despite broad similarities in number and structure of antennal glands, the results revealed interspecific differences with regard to overall shape, complexity, and relative size of the reservoirs as well as the number of the surrounding gland cell units. Mapping the morphology of all species studied so far on the phylogeny (that parallels geographical distribution) revealed that related species share similarities in gland morphology, but there are notable differences between lineages. In particular, compared to the North American species the European and African species possess more complex gland structures with a higher number of gland cells. We discuss morphological, ecological, and physiological aspects and provide scenarios for the evolution of the antennal glands of the Philanthini as symbiont cultivation organs. [ABSTRACT FROM AUTHOR]

The increasing resistance of human pathogens severely limits the efficacy of antibiotics in medicine, yet many animals, including solitary beewolf wasps, successfully engage in defensive alliances with antibiotic-producing bacteria for millions of years. Here, we report on the in situ production of 49 derivatives belonging to three antibiotic compound classes (45 piericidin derivatives, 3 streptochlorin derivatives, and nigericin) by the symbionts of 25 beewolf host species and subspecies, spanning 68 million years of evolution. Despite a high degree of qualitative stability in the antibiotic mixture, we found consistent quantitative differences between species and across geographic localities, presumably reflecting adaptations to combat local pathogen communities. Antimicrobial bioassays with the three main components and in silico predictions based on the structure and specificity in polyketide synthase domains of the piericidin biosynthesis gene cluster yield insights into the mechanistic basis and ecoevolutionary implications of producing a complex mixture of antimicrobial compounds in a natural setting. [ABSTRACT FROM AUTHOR]

Background: Sexual selection is thought to promote evolutionary changes and diversification. However, the impact of sexual selection in relation to other selective forces is difficult to evaluate. Male digger wasps of the tribe Philanthini (Hymenoptera, Philanthinae) scent mark territories to attract receptive females. Consequently, the organs for production and storage of the marking secretion, the mandibular gland (MG) and the postpharyngeal gland (PPG), are subject to sexual selection. In female Philanthini, these glands are most likely solely subject to natural selection and show very little morphological diversity. According to the hypothesis that sexual selection drives interspecific diversity, we predicted that the MG and PPG show higher interspecific variation in males than in females. Using histological methods, 3D-reconstructions, and multivariate statistical analysis of morphological characters, we conducted a comparative analysis of the MG and the PPG in males of 30 species of Philanthini and three species of the Cercerini and Aphilanthopsini, two related tribes within the Philanthinae. Results: We found substantial interspecific diversity in gland morphology with regard to gland incidence, size, shape and the type of associated secretory cells. Overall there was a phylogenetic trend: Ensuing from the large MGs and small PPGs of male Cercerini and Aphilanthopsini, the size and complexity of the MG was reduced in male Philanthini, while their PPG became considerably enlarged, substantially more complex, and associated with an apparently novel type of secretory cells. In some clades of the Philanthini the MG was even lost and entirely replaced by the PPG. However, several species showed reversals of and exceptions from this trend. Head gland morphology was significantly more diverse among male than among female Philanthinae. Conclusion: Our results show considerable variation in male head glands including the loss of an entire gland system and the evolution of a novel kind of secretory cells, confirming the prediction that interspecific diversity in head gland morphology is higher in male than in female Philanthini. We discuss possible causes for the remarkable evolutionary changes in males and we conclude that this high diversity has been caused by sexual selection. [ABSTRACT FROM AUTHOR]

Hydrocarbons (HCs) fulfil indispensable functions in insects, protecting against desiccation and serving chemical communication. However, the link between composition and function, and the selection pressures shaping HC profiles remain poorly understood. Beewolf digger wasps (Hymenoptera: Crabronidae) use an antennal gland secretion rich in linear unsaturated HCs to form a hydrophobic barrier around their defensive bacterial symbiont, protecting it from brood cell fumigation by toxic egg-produced nitric oxide (NO). Virtually identical HC compositions mediate desiccation protection and prey preservation from moulding in underground beewolf brood cells. It is unknown whether this composition presents an optimized adaptation to all functions, or a compromise due to conflicting selection pressures. Here, we reconstitute the NO barrier with single and binary combinations of synthetic linear saturated and unsaturated HCs, corresponding to HCs found in beewolves. The results show that pure alkanes as well as 3 : 1 mixtures of alkanes and alkenes resembling the composition of beewolf HCs form efficient protective barriers against NO, indicating that protection can be achieved by different mixtures of HCs. Since in vitro assays with symbiont cultures from different beewolf hosts indicate widespread NO sensitivity, HC-mediated protection from NO is likely important across Philanthini wasps. We conclude that HC-mediated protection of the symbiont from NO does not exert a conflicting selection pressure on the multifunctional HC profile of beewolves.

Background: Insects have evolved a wide range of mechanisms to defend themselves and their offspring against antagonists. One of these strategies involves the utilization of antimicrobial compounds provided by symbiotic bacteria to protect the host or its nutritional resources from pathogens and parasites. In the symbiosis of the solitary digger wasp, Philanthus triangulum (Hymenoptera, Crabronidae), the bacterial symbiont 'Candidatus Streptomyces philanthi' defends the developing larvae against pathogens by producing a mixture of at least nine antimicrobial substances on the cocoon surface. This antibiotic cocktail inhibits the growth of a broad range of detrimental fungi and bacteria, thereby significantly enhancing the offspring's survival probability. Results: Here we show that the production of antimicrobial compounds by the beewolf symbionts is confined to the first two weeks after cocoon spinning, leading to a high concentration of piericidins and streptochlorin on the cocoon surface. Expression profiling of housekeeping, sporulation, and antibiotic biosynthesis genes indicates that antibiotic production coincides with morphological differentiation that enables the symbionts to survive the nutrient-limited conditions on the beewolf cocoon. The antibiotic substances remain stable on the cocoon surface for the entire duration of the beewolf's hibernation period, demonstrating that the compounds are resistant against environmental influences. Conclusions: The antibiotic production by the beewolf symbionts serves as a reliable protection for the wasp offspring against pathogenic microorganisms during the long and unpredictable developmental phase in the subterranean brood cells. Thus, the beewolf-Streptomyces symbiosis provides one of the rare examples of antibiotics serving as an efficient defense in the natural environment and may aid in devising new strategies for the utilization of antibiotic combination therapies in human medicine against increasingly resistant bacterial and fungal pathogens. [ABSTRACT FROM AUTHOR]

Microorganisms are ubiquitous and key selective agents in parental care behaviour. Various animal species have thus evolved diverse means to prevent and combat detrimental effects of microbial competitors and pathogens on their offspring. The European beewolf, Philanthus triangulum, is a solitary crabronid wasp that stores paralysed honeybees as larval provisions in subterranean nests. In the soil the highly nutritious provisions can be attacked by a large number of microorganisms. We investigated the effect of fungal infestations of larval provisions on the reproductive success of beewolves. Although fungal infestations reduced larval survival, female beewolves largely eliminated this effect by embalming larval provisions with ample amounts of hydrocarbons. However, this came at the cost of a reduced ability to apply hydrocarbons to the provisions of future offspring. This reduced investment in embalming resulted in a higher risk of mould infestations. Embalming of the prey in P. triangulum thus meets the criterion of parental investment and females have to balance this investment of hydrocarbons in current and future offspring to maximize their lifetime reproductive success. [Copyright &y& Elsevier]

Several insect taxa have evolved symbioses with actinobacteria that protect the host or its nutritional resources against pathogens. Digger wasps of the genus Philanthus (‘beewolves’; Hymenoptera, Crabronidae) cultivate ‘ Candidatus Streptomyces philanthi’ ( Ca. S. philanthi) in specialized antennal glands and transfer them to subterranean brood cells, where the symbionts provide protection for the beewolf larva against pathogens by producing a cocktail of antibiotic substances. The present study investigates the occurrence of antennal symbionts in two species of the genus Trachypus, which is the closest relative to Philanthus. Cross sections of the antennae from females of both Trachypus denticollis and Trachypus boharti reveal bacteria-containing gland reservoirs that are morphologically very similar to those found in Philanthus spp. Polymerase chain reaction-based screens with specific primers, sequencing of the partial 16S rRNA gene, and fluorescence in situ hybridization confirm the presence of close relatives of ‘ Ca. S. philanthi’ in T. denticollis and T. boharti. However, 16S rRNA sequence divergence between Trachypus spp. and Philanthus spp. symbionts is much higher for T. boharti than for T. denticollis, suggesting that horizontal transmission and/or de novo uptake of symbionts from the environment occurs occasionally. The results obtained indicate that the protective symbiosis with antennal actinobacteria is older and more widespread than previously recognized and occurs in at least two genera of digger wasps that comprise approximately 170 species. [ABSTRACT FROM AUTHOR]

Abstract  Females of the European beewolf, Philanthus triangulum, possess a large glove-shaped gland in the head, the postpharyngeal gland (PPG). They apply the content of the PPG to their prey, paralyzed honeybees, where it delays fungal infestation. Here, we describe the chemical composition of the gland by using combined GC-MS, GC-FTIR, and derivatization. The PPG of beewolves contains mainly long-chain unsaturated hydrocarbons (C23–C33), lower amounts of saturated hydrocarbons (C14–C33), and minor amounts of methyl-branched hydrocarbons (C17–C31). Additionally, the hexane-soluble gland content is comprised of small amounts of an unsaturated C25 alcohol, an unknown sesquiterpene, an octadecenylmethylester, and several long-chain saturated (C25, C27) and unsaturated (C23–C27) ketones, some of which have not yet been reported as natural products. Surprisingly, we found a dimorphism with regard to the major component of the PPG with some females having (Z)-9-pentacosene, whereas others have (Z)-9-heptacosene as their predominant component. The biological relevance of the compounds for the prevention of fungal growth on the prey and the significance of the chemical dimorphism are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The postpharyngeal gland has long been thought to occur only in ants. Here we characterize, by use of light and electron microscopy as well as 3D reconstruction based on nuclear magnetic resonance (NMR) imaging data, a large cephalic gland reservoir of males of a solitary digger wasp, the European beewolf, Philanthus triangulum. Several lines of evidence suggest that this reservoir is a postpharyngeal gland. The gland reservoir originates from the posterior part of the pharynx and consists of two pairs of unbranched tubular structures that occupy a large portion of the head capsule. Its wall is composed of a unicellular epithelium that is lined by a cuticle. The gland contains a blend of hydrocarbons and compounds with functional groups, and we show that the hydrocarbon fraction of the pheromone is congruent with the hydrocarbons on the cuticle. We discuss the implications of our findings for the evolution of the postpharyngeal gland in ants. [Copyright &y& Elsevier]

Abstract??Ground-nesting animals share their habitat with countless microorganisms that can play important roles as pathogens or competitors for food resources. Thus, species that store food in the soil, either for themselves or for their progeny, must protect these resources against microbial degradation. Females of the European beewolf,Philanthus triangulum, hunt honeybees as provisions for their brood and store the paralyzed prey in their subterranean nests. A previous study had shown that females lick the surface of prey before oviposition and that this licking treatment delays mold growth. Here, we showed that females apply large amounts of a secretion from their postpharyngeal glands onto the surface of their prey during the licking behavior. Inhibition-zone assays showed that comparatively large amounts of the gland secretion had no direct antimycotic effect. We discuss our findings with regard to other possible mechanisms of the postpharyngeal gland secretion against fungal growth. [ABSTRACT FROM AUTHOR]

We studied the adult behavior, oviposition, and larval and pupal development of Hoplia philanthus Füessly (Scarabaeidae: Melolonthinae) in the field and laboratory in Belgium. Adult emergence was observed in the first week of June 2000, 2001, and 2002, peaked ≈2 wk later, and continued until the last week of the month. The average sex ratio of emerging adults was 1.3:1 (male and females) during the collection period. Adults were observed feeding mainly on leaves of Betula utilis variety jacquemontii (B. u. Doorenbos) and Carpinus betulus L. During the day, H. philanthus adults were most active at 1400 hours (CMT + 1.00). Oviposition started in the last week of June and lasted until the end of July. Each female deposited ≈25-40 white eggs at a depth of 10-15 cm in soil. Eggs hatched 28 ± 5 d after being laid at an average monthly soil temperature of 18.1°C. Three larval instars could be discerned by head capsule width; all larval instars fed on grass roots. The first-instar larvae were found in the last week of July 2000; second instars appeared mostly in the second week of September 2000 and could be found until May 2001. Third instars were found from the second week of June 2001 until April 2002. Pupae could be found from the first week of May until the end of the month. The duration of the pupal stage was 28 ± 5 d at an average monthly soil temperature of 16.5°C. According to these observations, H. philanthus has a 2-yr life cycle. [ABSTRACT FROM AUTHOR]

We report on a field study of the behavioural ecology of Megaselia oxybelorum Schmitz at nest aggregations of its hosts, the digger wasps Philanthus triangulum F. and Cerceris arenaria L. (Hymenoptera: Crabronidae). The flies flew across the P. triangulum nesting site both as single individuals and as females and males paired in copula, and the former case was recorded more than twice as often as the latter, while only single individuals were recorded at the C. arenaria site. Individuals both alone and in copula were seen at the P. triangulum site during the day roughly coinciding with the host provisioning activity, while at the C. arenaria site the fly's daily activity followed a bimodal trend in contrast to the normal distribution of the host provisioning. Visits of host nests were frequent at the P. triangulum site and null at the C. arenaria site. Single individuals spent less than 1 min inside a nest, while a female entering while still in copula spent generally 1–3 min inside, males exiting after 1–5 s, showing that only in this second case was an oviposition possible. The number of Megaselia oxybelorum increased with increasing host nest density and decreasing nearest neighbour distances of nests. Behavioural patterns of M. oxybelorum, when compared to other Megaselia spp. associated with fossorial Hymenoptera, showed differences possibly related to the biology of the hosts. In addition, some morphological variation within and between host sites are discussed. [ABSTRACT FROM AUTHOR]

The article reports on the identification of a Steinernema species as found in a infected third-instar Hoplia philanthus in Belgium. According to the report that the nematodes were identified and isolated according to a selection of morphological and morphometrical criteria. The isolated nematodes showed the typical pattern of steinernematids.

The genus Melaloncha Brues is defined and groundplan character states established based on outgroup comparison with Phalacrotophora Enderlein and Melittophora Brues. Major groupings within Melaloncha are recognized, and two subgenera are established: Udamochiras Enderlein (type species M. colossia (Enderlein)) and Melaloncha s.s. (type species M. pulchella Brues). Subgenus Udamochiras is revised and 42 species are recognized, including the following 33 new to science: M. anaticula, M. angustifrons, M. apicula, M. aprica, M. basella, M. biseta, M. brevicarina, M. carinata, M. compressicauda, M. exigua, M. falcata, M. flavilata, M. hamata, M. hansoni, M. horologia, M. individa, M. lobata, M. maculifrons, M. parkeri, M. paxilla, M. premordica, M. rhampha, M. rhypopoda, M. rostrata, M. sinuosa, M. spatula, M. spicula, M. triangularis, M. trua, M. valeria, M. vargasi, M. villosa, M. woodi. Melaloncha simillima Borgmeier is removed from synonymy with M. piliapex Borgmeier and reinstated as a separate species; lectotypes are designated for both. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 140, 1−42 [ABSTRACT FROM AUTHOR]

The chemical composition and functional significance of pheromones of solitary Hymenoptera is much less well known compared to social species. Males of the genus Philanthus (Sphecidae) are territorial and scent mark their territories to attract females. Because of inconsistent results of earlier studies, we reanalyzed the content of the cephalic glands of male European bee- wolves, Philanthus triangulum F. Besides a variety of alkanes and alkenes, four major compounds were found. Two of these, (Z)-11-eicosen-1-oI and (Z)-10- nonadecen-2-one, had been previously described as constituents of the cephalic glands. We identified 1-octadecanol as a new component of the cephalic gland, and a fourth compound, enantiopure (S)-2,3-dihydrofarnesoic acid, was identified for the first time in nature. Structural elucidation and enantiomeric analysis were performed by HRGC-MS and HRGC-FTLR as well as enantioselective gas chromatography and by means of authentic reference compounds. Occurrence and function of the four compounds in insect chemistry are discussed. [ABSTRACT FROM AUTHOR]

Summary1. Females of the European beewolf Philanthus triangulum (Hymenoptera, Sphecidae) provision brood cells with paralysed honeybees as larval food. Because brood cells are located in warm, humid locations there is a high risk of microbial decomposition of the provisions. Low incidence of fungus infestation (Aspergillus sp.) in nests in the field suggested the presence of an anti-fungal adaptation. 2. To test whether the paralysis caused the protection from fungus infestation, the timing of fungus growth on bees that were freeze-killed, paralysed but not provisioned, and provisioned regularly by beewolf females was determined. Fungus growth was first detected on freeze-killed bees, followed by paralysed but not provisioned bees. By contrast, fungus growth on provisioned bees was delayed greatly or even absent. Thus, paralysis alone is much less efficient in delaying fungus growth than is regular provisioning. 3. Observations of beewolves in their nests revealed that females lick the body surface of their prey very thoroughly during the period of excavation of the brood cell. 4. To separate the effect of a possible anti-fungal property of the brood cell and the licking of the bees, a second experiment was conducted. Timing of fungus growth on paralysed bees did not differ between artificial and original brood cells. By contrast, fungus growth on bees that had been provisioned by a female but were transferred to artificial brood cells was delayed significantly. Thus, the treatment of the bees by the female wasp but not the brood cell caused the delay in fungus growth. 5. Beewolf females most probably apply anti-fungal chemicals to the cuticle of their prey. This is the first demonstration of the mechanism involved in the preservation of provisions in a hunting wasp. Some kind of preservation of prey as a component of parental care is probably widespread among hunting wasps and might have been a prerequisite for the evolution of mass provisioning. [ABSTRACT FROM AUTHOR]

Assesses the behavior of European beewolves to determine how the size of the female affects breeding and provision of food. How size can constrain females; Reference to males receiving two thirds of food provisions; What kind of food females hunt for; How food provision is stored.