Stingless bees (<Emphasis Type="Italic">Scaptotrigona pectoralis</Emphasis>) learn foreign trail pheromones and use them to find food

Foragers of several species of stingless bees (Hymenoptera, Apidae and Meliponini) deposit pheromone marks in the vegetation to guide nestmates to new food sources. These pheromones are produced in the labial glands and are nest and species specific. Thus, an important question is how recruited foragers recognize their nestmates’ pheromone in the field. We tested whether naïve workers learn a specific trail pheromone composition while being recruited by nestmates inside the hive in the species Scaptotrigona pectoralis. We installed artificial scent trails branching off from trails deposited by recruiting foragers and registered whether newly recruited bees follow these trails. The artificial trails were baited with trail pheromones of workers collected from foreign S. pectoralis colonies. When the same foreign trail pheromone was presented inside the experimental hives while recruitment took place a significant higher number of bees followed the artificial trails than in experiments without intranidal presentation. Our results demonstrate that recruits of S. pectoralis can learn the composition of specific trail pheromone bouquets inside the nest and subsequently follow this pheromone in the field. We, therefore, suggest that trail pheromone recognition in S. pectoralis is based on a flexible learning process rather than being a genetically fixed behaviour.     

Volatile cephalic substances of the stingless bees, Trigona mexicana and Trigona pectoralis

Extracts of the heads of the stingless bees, Trigona mexicana and T. pectoralis, contain mixtures of compounds that are identifiable by gas chromatography and mass spectrometry. These compounds form homologous series of aliphatic alcohols and ketones with an odd number of carbon atoms and functional groups at the 2-position. The alcohols and the ketones range from 7 to 17 carbon atoms. Benzaldehyde and a nitrogen containing compound are also present in the mixtures. The series of compounds from the two species are nearly identical qualitatively. They differ in the absence of 2-undecanol and 2-pentadecanol from the extracts of T. mexicana and T. pectoralis, respectively. The highest concentration of material is found in the 7-carbon fraction in T. mexicana and in the 13 to 15 carbon range in T. pectoralis. There is a major difference in the relative concentration of 2-heptanol and 2-heptanone in the two species with the concentration of the alcohol being one-fourth that of 2-heptanone in T. mexicana and ten times greater than the ketones in T. pectoralis.Both the alcohols and ketones are alarm pheromones. The alcohols are more active in inducing attack by the bees than are the ketones, but a mixture of the ketones and benzaldehyde was very active.     

Secretions of stingless bees: cephalic secretions of two Frieseomelitta species

Gas chromatographic and mass spectrometric analysis of the volatile compounds in the mandibular glands of Frieseomelitta varia and the heads of Frieseomelitta silvestrii have revealed relatively simple or more complex mixtures of volatile oxygenated compounds. 2-Alkanols were found to be important components for both species. In F. varia the composition was essentially the same in samples from two widely separated areas and there were small differences between callows and mature, foraging bees. The first electroantennographic studies on stingless bees, using hexane extracts of heads of both species, have demonstrated a response in the workers’ antennae to these, as well as to the pure compounds 2-heptanol and 2-nonanol .     

The cuticular profiles of Australian stingless bees are shaped by resin of the eucalypt tree Corymbia torelliana

Bees are known to collect pollen and nectar to provide their larvae and themselves with food. That bees, especially the tropical stingless bees (Apidae: Meliponini), also collect plant resins has, however, been barely addressed in scientific studies on resource use in bees. Resins are used for nest construction, nest maintenance and nest defence. Furthermore, some South‐East Asian species transfer resin‐derived terpenes to their cuticular profiles. The resin requirement of bees is in turn used by certain plant species, which attract bees either for pollination by providing resin in their inflorescences, or for seed dispersal by providing resin in their seed capsules (mellitochory). Mellitochory is found in the eucalypt tree Corymbia torelliana, the resin of which is collected by Australian stingless bees. We investigated how the interaction between C. torelliana and resin‐collecting bees affects the chemical ecology of two Australian stingless bee genera by comparing the chemical profiles of eight bee species with resin from C. torelliana fruits. The two bee genera differed significantly in their chemical profiles. Similar to South‐East Asian stingless bees, 51% of all compounds on the body surfaces of the five Tetragonula species were most likely derived from plant resins. Up to 32 compounds were identical with compounds from C. torelliana resin, suggesting that Tetragonula species include C. torelliana compounds in their chemical profiles. By contrast, few or none resinous compounds were found on the body surfaces of the three Austroplebeia species sampled. However, one prominent but as yet unknown substance was found in both C. torelliana resin and the chemical profiles of all Tetragonula and four Austroplebeia colonies sampled, suggesting that most colonies (76%) gathered resin from C. torelliana. Hence, C. torelliana resin may be commonly collected by Australian stingless bees and, along with resins from other plant species, shape their chemical ecology.     

Temporal Response of Foragers and Guards of Two Stingless Bee Species to Cephalic Compounds of the Robber Bee <Emphasis Type="Italic">Lestrimelitta niitkib</Emphasis> (Ayala) (Hymenoptera,Apidae)

Lestrimelitta spp. are stingless bees that steal food and nesting materials from other highly social bees to survive. Though most of their victim species respond, either aggressively or submissively, to cephalic components of Lestrimelitta, little is known about if such response changes at some point during extended periods of exposure. Moreover, potential synergistic effects due to a mixture of victim’s alarm/defense pheromones and Lestrimelitta mandibular pheromones, like in an actual attack, have not been examined so far. In this paper, we investigated the response of two species of non-robber stingless bees, Scaptotrigona mexicana (Guérin) and Tetragonisca angustula (Latreille), to (a) cephalic compounds from crushed heads of nestmates, (b) cephalic compounds of Lestrimelitta niitkib (Ayala), and (c) a mixture of (a) and (b). We found that even though T. angustula did not react to nestmates’ crushed head, its response towards L. niitkib cephalic compounds was stronger and lasted longer than that of S. mexicana. Interestingly, the addition of crushed heads of the non-robber species to L. niitkib crushed heads caused no significant increase in the alarm response of both species. It may be that the absence of an alarm pheromone in T. angustula made this species more receptive to extraneous odors, which is not the case for S. mexicana; however, more species must be studied to elucidate any pattern regarding the absence/presence of alarm pheromones and the corresponding response to intruders’ pheromones.     

Temporal dynamics of facultative social parasitism in bumble bees (Hymenoptera: Apidae)

Parasitical behaviour is thought to play an important, yet so far largely unknown role in the evolution and maintenance of insect sociality. In this study, the influence of interspecific, facultative social parasitism upon bumble bee, Bombus, nesting biology was explored. Queens of B. affinis were introduced into 38 various-sized laboratory colonies of B. terricola. Foreign queens were very successful at killing the resident queen and usurping pre-worker nests (77% wins), although usurpation success decreased to 30% in colonies that contained workers. In addition, B. affinis queens were unable to suppress ovarian development in B. terricola workers that emerged prior to nest usurpation, resulting in the eventual death or expulsion of the foreign queen. In contrast, ovarian development was supporessed in workers that eclosed in the presence of a foreign queen, and in workers that were less than 5 h old when confined in small experimental boxes with a B. affinis queen. Foreign queens that usurped a nest prior to worker emergence were assisted by B. terricola workers, and achieved similar reproductive success when compared to a cohort of 22 B. affinis queens that initiated their own nests in the laboratory. These results suggest that there are periods in the ontogeny of Bombus nest defence, recognition and dominance during which bees are sensitive to the effects of nest parasitism. In bumble bees, and in other social insects, individuals of some species may exploit these weaknesses for their own reproductive benefit.     

Ophiostomatoid fungi can emit the bark beetle pheromone verbenone and other semiochemicals in media amended with various pine chemicals and beetle-released compounds

Fungal volatile compounds can mediate fungal-insect interactions. Whether fungi can emit insect pheromones and how volatile chemicals change in response to chemicals the fungi naturally encounter is poorly understood. We analyzed volatiles emitted by Grosmannia clavigera (symbiont of the mountain pine beetle) and Ophiostoma ips (symbiont of the pine engraver beetle) growing in liquid media amended with compounds that the fungi naturally encounter: (−)-α-pinene, (+)-α-pinene, (−)-trans-verbenol, verbenone, or ipsdienol. Nine volatile compounds were identified among the fungal and amendment treatments. Volatiles qualitatively and quantitatively differed between fungal species and among amendment treatments. The bark beetle anti-aggregation pheromone (−)-verbenone was detected from both fungi growing in (−)-trans-verbenol-amended media. G. clavigera and O. ips can emit beetle pheromones and other beetle semiochemicals, suggesting that ophiostomatoid fungi could contribute to the chemical ecology of bark beetles. However, such contributions could be modulated by the presence of other environmental chemicals.     

Smelling like resin: terpenoids account for species-specific cuticular profiles in Southeast-Asian stingless bees

Insects may be unique in having a cuticle with a species-specific chemical profile. In social insects, colony survival depends not only on species-specific but also on colony-specific cuticular compounds with hydrocarbons playing an important role in the communication systems of ants, termites, wasps and bees. We investigated inter- and intraspecific differences in the composition of compounds found on the body surface of seven paleotropical stingless bee species (Apidae: Meliponini) at two different sites in Borneo (Sabah, Malaysia). Besides hydrocarbons, the body surface of all seven stingless bee species comprised terpenoid compounds, a substance class that has not been reported for chemical profiles of any social insect so far. Moreover, the chemical profile of some species differed fundamentally in the composition of terpenoids with one group (e.g. sesquiterpenes) being present in one species, but missing in another. Chemical profiles of different colonies from the same species showed the same hydrocarbon- and terpenoid compounds over different regions, as tested for Tetragonilla collina and Tetragonula melanocephala. However, chemical profiles differed quantitatively between the different colonies especially in T. melanocephala. It is likely that the terpenoids are derived from plant resins because stingless bees are known to collect and use large amounts of resins for nest construction and defence, suggesting an environmental origin of the terpenoids in the chemical profile of paleotropical stingless bees.     

Interaction between oil-collecting bees and seven species of Plantaginaceae

Oil-bee/oil-flower mutualism evolved through multiple gains and losses of the ability to produce floral oil in plants and to collect it in bees. Around 2000 plant species are known to produce floral oils that are collected by roughly 450 bee species, which use them for the construction of nests and for the larval food. The Plantaginaceae contain several Neotropical species that produce floral oils, the main reward offered by these plants. In the genera Angelonia, Basistemon, Monopera and Monttea, mainly associated with Centris bees, the floral oil is produced in trichomes that are located in the inner corolla. The pollinators of a few species in this neotropical clade of Plantaginaceae are known, and the role of flower morphology as well as the requirements from pollinators and the role of other groups of bees in the pollination of these flowers remains unclear. In this paper we provide a list of the flower visitors of seven Plantaginaceae species (six Angelonia species and Basistemon silvaticus) analyzing their behavior to highlight the legitimate pollinators and illustrating little known aspects of flower morphology and oil-collecting apparatuses of the bees. Two general morphological patterns were observed in the Angelonia flowers: deep corolla tube with short lobes, and short corolla tube with long lobes. Corolla tubes of different length result in pollen adherence to different parts of the insect body. The six Angelonia species and B. silvaticus flowers were visited by 25 oil-collecting bee species (10 Centris, 11 Tapinotaspidini and 4 Tetrapedia species), the majority acting as legitimate visitors. The flowers were also visited by illegitimate bee pollinators, which collected pollen but do not transfer it to the female organ. Specialized collectors of Plantaginaceae floral oils present modifications on the first pair of legs, mainly in the basitarsi but also extended to the tarsomeres. The new records of Tapinotaspidini and Centridini species acting as specialized pollinators of Plantaginaceae suggest that there is a geographic variation in the pollinators of the same plant species, and that the evolutionary scenario of the historical relationships between oil-collecting bees and floral oil producing plants is more complex than previously considered.     

Ground-nesting bees determine the location of their nest relative to a landmark by other than angular size cues

Bees and wasps acquire a visual representation of their nest's environment and use it to locate their nest when they return from foraging trips. This representation contains among other features cues to the distance of near-by landmarks. We worked with two species of ground-nesting bees, Lasioglossum malachurum (Hymenoptera: Halictidae), Dasypoda hirtipes (Hymenoptera: Melittidae) and asked which cues to landmark distance they use during homing. Bees learned to associate a single cylindrical landmark with their nest's location. We subsequently tested returning bees with landmarks of different sizes and thus introduced large discrepancies between the angular size of the landmark as seen from the nest during training and its distance from the nest. The bees' search behaviour and their choice of dummy nest entrances show that both species of ground-nesting bees consistently search for their nest at the learned distance from landmarks. The influence of the apparent size of landmarks on the bees' search and choice behaviour is comparatively weak. We suggest that the bees exploit cues derived from the apparent speed of the landmark's image at their retina for distance evaluation.     

Nesting aggregation as a predictor of brood parasitism in mason bees (Osmia spp.)

1. Parasitism can be an important source of mortality for insect populations; however, we know little about the factors influencing vulnerability of wild bees to parasites. Mason bees (genus Osmia; Hymenoptera: Megachilidae) are important pollinators of crops and wild plants and are vulnerable to attack by brood parasites. High nest densities may increase rates of brood parasitism by attracting disproportionate numbers of parasites. 2. Three years of field observations from multiple sites were analysed to assess whether mason bee brood parasitism increased with host density. Mason bees were allowed to nest in artificial nesting blocks and establish natural variation in nesting density. Nest cells constructed by bees were checked for the presence of parasite eggs. 3. Parasitism of nest cells strongly increased with the number of actively nesting bees at a nesting block. Mason bees showed no preference for nesting in blocks that were occupied or unoccupied by other mason bees. Parasitism also increased with the number of days a nest was provisioned and decreased over the course of the season. Nest cells constructed last in a nest were significantly more parasitised than inner cells, despite being sealed against invasions. 4. These findings show positively density‐dependent parasitism in mason bees. They also suggest that bees terminate parasitised nests, causing parasitised cells to become outermost nest cells – a behaviour that may represent a defence against parasites. Our results have implications for the management of mason bees as agricultural pollinators, as cultivating them at high densities could reduce offspring survival.     

Pollen diets and niche overlap of honey bees and native bees in protected areas

The decline of both managed and wild bee populations has been extensively reported for over a decade now, with growing concerns amongst the scientific community. Also, evidence is growing that both managed and feral honey bees may exacerbate threats to wild bees. In Australia, there are over 1600 native bee species and introduced European honey bees (Apis mellifera) have established throughout most landscapes. There is a major gap in knowledge of the interactions between honey bees and native bees in Australian landscapes, especially floral resource use.Here we report on the pollen diets of wild bees in protected areas of coastal heathland, an ecosystem characterised by mass flowering in late winter and spring. We sampled bees within three sites and DNA metabarcoding was used to compare the pollen diets of honey bees and native bees. We recorded 2, 772 bees in total, with 13 genera and 18 described species identified. Apis mellifera was the most common species across all locations, accounting for 42% of all bees collected. Native bee genera included eusocial Tetragonula (stingless bees) (37%), and semi-social Exoneura and Braunsapis (19.8% combined). Metabarcoding data revealed both Tetragonula and honey bees have wide foraging patterns, and the bipartite network overall was highly generalised (H₂’ = 0.24). Individual honey bees carried pollen of 7–29 plant species, and significantly more species than all other bees. We found niche overlap in the diets of honey bees and native bees generally (0.42), and strongest overlap with stingless bees (0.70) and species of Braunsapis (0.62). A surprising finding was that many species carried pollen from Restionaceae and Cyperaceae, families generally considered to be predominantly wind-pollinated in Australia. Our study showed introduced honey bee use of resources overlaps with that of native bees in protected heathlands, but there are clear differences in their diet preferences.     

Variation in composition of two bumble bee species across communities affects nectar robbing but maintains pollinator visitation rate to an alpine plant,Salvia przewalskii

1. In many flowering plants, bumble bees may forage as both pollinators and nectar robbers. This mixed foraging behaviour may be influenced by community context and consequently, potentially affect pollination of the focal plant. 2. Salvia przewalskii is both pollinated and robbed exclusively by bumble bees. In the present study area, it was legitimately visited by two species of bumble bees with different tongue length, Bombus friseanus and Bombus religiosus, but it was only robbed by Bombus friseanus, the shorter‐tongued bumble bee. The intensity of nectar robbing and pollinator visitation rate to the plant were investigated across 26 communities in the Hengduan Mountains in East Himalaya during a 2‐year project. For each of these communities, the floral diversity, and the population size and floral resource of S. przewalskii were quantified. The abundances of the two bumble bee species were also recorded. 3. Both nectar robbing and pollinator visitation rate were influenced by floral diversity. However, pollinator visitation rate was not affected by nectar robbing. The results revealed that relative abundance of the two bumble bee species significantly influenced the incidence of nectar robbing but not the pollinator visitation rate. Increased abundance of B. religiosus, the legitimate visitors, exacerbated nectar robbing, possibly by causing B. friseanus to shift to robbing; however, pollinator visitation remained at a relatively high level. 4. The results may help to explain the persistence of both nectar robbing and pollination, and suggest that, in comparison to pollination, nectar robbing is a more unstable event in a community.     

Queen-worker conflict and social parasitism in bumble bees (Hymenoptera: Apidae)

Psithyrus ashtoni (Hymenoptera: Apidae) is an obligate, workerless bumble, bee social parasite which invades nests of Bombus affinis. Although parasites are limited by host worker defence to invading very small colonies, there is considerable flexibility in the way parasites control host brood bionomics once they are accepted inside the nest. A study of 46 parasitized and 22 non-parasitized laboratory colonies of B. affinis showed that P. ashtoni females cohabited with host queens and workers while the worker force increased, but not to the maximum normally achieved in non-parasitized nests. While colony reproductive success was correlated with the number of workers reared, parasites risked being killed or ejected from the comb by workers, after the queen had lost dominance. Host bees usually succeeded in rearing offspring, and Psithyrus reproductive success was related to the ability of parasites to control proportional investment in the two species. In addition to displacing P. ashtoni females, host bees ate the eggs of parasites and ejected their larvae. These behaviours were also exhibited by workers in the later stages of development of non-parasitized colonies. These results indicate that social parasites are at least partially subject to the conflict of genetic self-interest between the queen and her workers which is believed to influence the control of reproductive investment in haplodiploid Bombus societies.     

Alarm communication in <Emphasis Type="Italic">Ropalidia</Emphasis> social wasps

Summary Alarm pheromones, chemical substances produced by social insects to alert the colony to threat, are the principal means by which colony defence is co-ordinated. We present the results of a study on alarm behaviour in 5 swarming species of wasps belonging to the genus Ropalidia. These species show a remarkably efficient strategy of alarm communication, including visual display and attack synchronization. We show that pheromones released from the venom gland play an important role in alarm recruitment in species belonging to the Ropalidia flavopicta group, but not in Ropalidia sumatrae. We analysed the contents of the venom reservoirs content of four of the studied species by gas chromatography-mass spectrometry. Glands were found to contain a complex mixture of volatile compounds as well as spiroacetals of higher molecular weight. Interestingly, despite all species producing similar chemical compounds from the venom gland, these were found to elicit alarm behaviour in only those species that build nest envelopes, suggesting a link between chemical release of alarm behaviour and the evolution of nest architecture in Ropalidia wasps.Received 19 August 2003; revised 29 February 2004; accepted 10 March 2004     

The role of Dufour's gland secretions in bees

ABSTRACT. Dufour's gland of bees is often hypertrophied and an extremely rich source of diverse natural products. In the ground-dwelling bees the secretion is mostly used for lining the brood cell with a hydrophobic lining. Whereas in several species the secretion is smeared on the cell walls without any modification, in others the hydrophobic lining is formed only after a chemical transformation of the secretion. The diversity of the chemical means by which hydrophobicity of the brood cells is achieved suggests that it has evolved repeatedly in the bees. In addition to lining their brood cells, several species use Dufour's gland secretion to mark their nest entrance. Analyses of single glands from various species reveal that each bee possesses its own individual composition, expressed in specific relative amounts of each component. Interestingly in the social halictid Evylaeus malachurum , nestmates (considered as sisters) are more similar to each other than non-related bees. The possible functional evolution of the glandular exudate from structural functions to communication and its implications for our understanding of eusociality in bees, is discussed.     

Applying geographic profiling used in the field of criminology for predicting the nest locations of bumble bees

We tested whether geographic profiling (GP) can predict multiple nest locations of bumble bees. GP was originally developed in the field of criminology for predicting the area where an offender most likely resides on the basis of the actual crime sites and the predefined probability of crime interaction. The predefined probability of crime interaction in the GP model depends on the distance of a site from an offender's residence. We applied GP for predicting nest locations, assuming that foraging and nest sites were the crime sites and the offenders’ residences, respectively. We identified the foraging and nest sites of the invasive species Bombus terrestris in 2004, 2005, and 2006. We fitted GP model coefficients to the field data of the foraging and nest sites, and used GP with the fitting coefficients. GP succeeded in predicting about 10-30% of actual nests. Sensitivity analysis showed that the predictability of the GP model mainly depended on the coefficient value of buffer zone, the distance at the mode of the foraging probability. GP will be able to predict the nest locations of bumble bees in other area by using the fitting coefficient values measured in this study. It will be possible to further improve the predictability of the GP model by considering food site preference and nest density.     

Genetic bases of tolerance to Varroa destructor in honey bees (Apis mellifera L.)

Currently, the Varroa destructor mite is the most serious parasite of honey bees (Apis mellifera) and has become a nearly cosmopolitan species. The mite not only causes damage by feeding on the haemolymph of honey bees, but it also transmits viruses, which have been implicated in colony collapse disorder. The major research goal has been to breed mite-tolerant honey bee lines in order to reduce the amount of pesticide used, because pesticides can promote the evolution of resistance in mites. In this review, we describe different behavioural traits and genes that may be part of the defence against the Varroa mite. Specifically, we review grooming behaviour, Varroa-sensitive hygiene and the suppression of mite reproduction. A large number of candidate genes have been identified by Quantitative Trait Loci studies, and through gene expression studies their function and effect have been elucidated. Results from the studies discussed can be used in apiary practice.     

The propolis of stingless bees: terpenes from the tibia of three Frieseomelitta species

The posterior tibia of foraging workers of three species of Frieseomelitta (Hymenoptera: Meliponinae) stingless bees have been shown to carry complex mixtures of plant-derived mono-, sesqui-, di- and tri-terpenes. These subtances were not found on the fore- or mid-legs, nor on other parts of the hind legs. F. silvestrii and F. silvestrii languida, when collecting, appear to exploit different plants for their resin even when housed in the same area. F. varia were found to be not collecting resin at the time of the initial sampling and were therefore sampled later. Mature foragers carry the resin. In the samples studied here, particularly prominent were the monoterpene α-pinene, the sesquiterpenes β-caryophyllene, α-cubebene, α- and γ-muurolene, γ-cadinene, germacrene-D, and elemol and the diterpenes manool and totarol The collected material is used for the resin placed around the entrance to their nests and is also mixed with wax, to produce the cerum used for the structures in the nest.     

PVC nest boxes are less at risk of occupancy by feral honey bees than timber nest boxes and natural hollows

Feral European Honey Bee (Apis mellifera) has been identified as a potential nest competitor for Australian hollow nesting species, but few studies have investigated the impact of feral honey bee competition on Threatened species. Our study used data from Glossy Black‐cockatoo (Calyptorhynchus lathami halmaturinus) nests on Kangaroo Island, monitored and managed over an 11‐year period, and found 12% of nests became occupied by feral honey bees during that period. Our results indicate that feral honey bees were less likely to occupy nest boxes made of PVC (5%) compared with wooden nest boxes (24%) or natural hollows in Eucalyptus trees (14%). The removal of feral honey bee hives from nests is a priority for long‐term conservation of glossy black‐cockatoos on Kangaroo Island. We recommend that PVC nest boxes are chosen for future nesting habitat restoration, due to the more frequent use of wooden nest boxes by feral honey bees.