A Sticky Affair: Resin Collection by Bornean Stingless Bees

Plant resins are used by stingless bees for nest construction and maintenance. To reveal factors that influence the bees' decision about where and when to collect resin, resin collection was studied in ten stingless bee species (Apidae, Meliponini) collecting resin at natural and artificially induced wounds of nine tree species in Borneo. Artificially induced wounds were found by bees within 1–2 d. The number of foragers at artificial wounds increased during the subsequent 5 d until resin secretion stopped or the resin hardened. At natural resin wounds, species identity and number of foragers remained constant during the observation period. Bees collected resin from some trees and ignored others. Agathis borneensis (Araucariaceae) was the most attractive resin source. The bees' visitation rate did not correlate significantly with resin wound size. Inter- and intraspecific aggression occurred at ten resin wounds. In Tetragonilla collina and Tetragonula melanocephala , we additionally recorded resin intake at colony entrances. The proportion of workers retuning with resin varied considerably between colonies. We observed attacks by ants at three of our eight focal colonies, which resulted in a significant increase in resin intake while the nest was under attack and until 1–2 d after the attack had stopped. The increase in resin collection triggered by ant attacks was even stronger than the increase following a manual destruction of the nest entrance tube.     

Bees for Development: Brazilian Survey Reveals How to Optimize Stingless Beekeeping

Stingless bees are an important asset to assure plant biodiversity in many natural ecosystems, and fulfill the growing agricultural demand for pollination. However, across developing countries stingless beekeeping remains an essentially informal activity, technical knowledge is scarce, and management practices lack standardization. Here we profited from the large diversity of stingless beekeepers found in Brazil to assess the impact of particular management practices on productivity and economic revenues from the commercialization of stingless bee products. Our study represents the first large-scale effort aiming at optimizing stingless beekeeping for honey/colony production based on quantitative data. Survey data from 251 beekeepers scattered across 20 Brazilian States revealed the influence of specific management practices and other confounding factors over productivity and income indicators. Specifically, our results highlight the importance of teaching beekeepers how to inspect and feed their colonies, how to multiply them and keep track of genetic lineages, how to harvest and preserve the honey, how to use vinegar traps to control infestation by parasitic flies, and how to add value by labeling honey containers. Furthermore, beekeeping experience and the network of known beekeepers were found to be key factors influencing productivity and income. Our work provides clear guidelines to optimize stingless beekeeping and help transform the activity into a powerful tool for sustainable development.     

Bioactive Attributes and Analysis of Electronic Nose Feature Signals of Colombian Stingless Bees Propolis

The volatile and non-volatile chemical composition and bioactivity of propolis from the species Apis mellifera has been widely studied, but there is very little knowledge regarding propolis of other bee species, which ultimately hinders their differentiation and potential use. In this work, 53 propolis samples of A. mellifera and four stingless bee species (Frieseomielitta sp., Melipona eburnea, Melipona sp., and Trigona sp.) were collected in Colombia. An electronic nose with 10 metal oxide semiconductor sensors (MOS) was used to generate a pattern of the representative volatile compounds of the samples. Ethanolic extracts were obtained to assess their antioxidant activity towards DPPH radical and ABTS radical cation, total phenolics, and color (CIELAB space). The results showed an overall similarity of the aromatic profiles between species. The antioxidant activity of Frieseomielitta sp. propolis was higher than that of A. mellifera and the other species, in correspondence with a higher phenolic content. CIELAB color parameter b* was the most differentiating variable among samples, indicating a variation of propolis colors between red and yellow. By combining the data from physico-chemical analysis and aromatic profile, it was possible to differentiate the propolis from each bee species, with the exception of those from Melipona sp. and Trigona sp., indicating their similarity. These results have practical significance since they are a starting point to recognizing and valuing native stingless bee propolis and their bioactive potential, which, in addition to geographical differentiation and further quality parameters evaluation, will enhance their commercial exploitation.     

A Comparative Study of Relational Learning Capacity in Honeybees (Apis mellifera) and Stingless Bees (Melipona rufiventris)

Background

Learning of arbitrary relations is the capacity to acquire knowledge about associations between events or stimuli that do not share any similarities, and use this knowledge to make behavioural choices. This capacity is well documented in humans and vertebrates, and there is some evidence it exists in the honeybee (Apis mellifera). However, little is known about whether the ability for relational learning extends to other invertebrates, although many insects have been shown to possess excellent learning capacities in spite of their small brains.

Methodology/Principal Findings

Using a symbolic matching-to-sample procedure, we show that the honeybee Apis mellifera rapidly learns arbitrary relations between colours and patterns, reaching 68.2% correct choice for pattern-colour relations and 73.3% for colour-pattern relations. However, Apis mellifera does not transfer this knowledge to the symmetrical relations when the stimulus order is reversed. A second bee species, the stingless bee Melipona rufiventris from Brazil, seems unable to learn the same arbitrary relations between colours and patterns, although it exhibits excellent discrimination learning.

Conclusions/Significance

Our results confirm that the capacity for learning arbitrary relations is not limited to vertebrates, but even insects with small brains can perform this learning task. Interestingly, it seems to be a species-specific ability. The disparity in relational learning performance between the two bee species we tested may be linked to their specific foraging and recruitment strategies, which evolved in adaptation to different environments.     

Resource Partitioning between Highly Eusocial Bees and Possible Impact of the Introduced Africanized Honey Bee on Native Stingless Bees in the Brazilian Atlantic Rainforest

The highly eusocial bee community of the neotropical Atlantic Rainforest was studied at Boracéia Biological Station in the state of São Paulo, Brazil. In this reserve, 17 species of stingless bees and the introduced Africanized honey bee were found, the latter being the most abundant flower visitor. Of all flowering plants, Asteraceae and Myrtaceae were particularly important as resources for bees. Trophic niche overlap between the various species of stingless bees is evident, and it was generally larger within the tribes Meliponini and Trigonini than between members of different tribes. Nevertheless, in the stingless bee community the competitive pressure is rather uniformly spread. The trophic niche of the Africanized honey bee can be positioned between those of Meliponini and Trigonini. Today this introduced species represents the main competitor in this bee community. However, its impact on native stingless bee populations is apparently buffered by mass-flowering trees which are the most important food plants of the indigenous highly eusocial bees.     

Effect of Australian Propolis from Stingless Bees (Tetragonula carbonaria) on Pre-Contracted Human and Porcine Isolated Arteries

Bee propolis is a mixture of plant resins and bee secretions. While bioactivity of honeybee propolis has been reported previously, information is limited on propolis from Australian stingless bees (Tetragonula carbonaria). The aim of this study was to investigate possible vasomodulatory effects of propolis in KCl-precontracted porcine coronary arteries using an ex vivo tissue bath assay. Polar extracts of propolis produced a dose-dependent relaxant response (EC₅₀=44.7±7.0 μg/ml), which was unaffected by endothelial denudation, suggesting a direct effect on smooth muscle. Propolis markedly attenuated a contractile response to Ca²⁺ in vessels that were depolarised with 60 mM KCl, in Ca²⁺-free Krebs solution. Propolis (160 µg/ml) reduced vascular tone in KCl pre-contracted vessels to near-baseline levels over 90 min, and this effect was partially reversible with 6h washout. Some loss in membrane integrity, but no loss in mitochondrial function was detected after 90 min exposure of human cultured umbilical vein endothelial cells to 160 µg/ml propolis. We conclude that Australian stingless bee (T. carbonaria) propolis relaxes porcine coronary artery in an endothelial-independent manner that involves inhibition of voltage-gated Ca²⁺ channels. This effect is partially and slowly reversible upon washout. Further studies are required to determine the therapeutic potential of Australian stingless bee propolis for conditions in which vascular supply is compromised.     

Number of Malpighian Tubules in Larvae and Adults of Stingless Bees (Hymenoptera: Apidae) from Amazonia

The number of Malpighian tubules in larvae and adults of bees is variable. Larvae of Apis mellifera L. have four Malpighian tubules, while adults have 100 tubules. In stingless bees, this number varies from four to eight. The objectives of this study were to provide characteristics of the Malpighian tubules as well as to quantify their number in larvae and adults of six species of Meliponinae, Melipona seminigra merrillae Cockerell, Melipona compressipes manaosensis Schwarz, Melipona rufiventris Lepeletier, Scaptotrigona Moure, Frieseomelitta Ihering, and Trigona williana Friese. Malpighian tubules were dissected from larvae and adults, measured, quantified, and maintained in microtubes with Dietrich??s solution. The numbers of Malpighian tubules were constant only for larvae of M. rufiventris (four and eight) and Scaptotrigona sp. (four). The most frequent number of tubules in the Melipona group was seven and eight in larvae, and 70 and 90 in adults. In the Trigona group were four and 20 to 40, for larvae and adults, respectively. The results showed differences in the number of Malpighian tubules among the species analyzed and also between the larvae and adults of the same species. Despite the variation observed, species of the group Melipona always have a larger number and longer Malpighian tubules in both larvae and adults as compared to the Trigona group, which may indicate an evolutionary trend of differentiation between these groups.     

Effect of Biotic Factors on the Spatial Distribution of Stingless Bees (Hymenoptera: Apidae, Meliponini) in Fragmented Neotropical Habitats

We recorded stingless bee colony abundance and nesting habits in three sites with different anthropogenic activities in the Soconusco region of Chiapas, Mexico: (1) agroforestry (7 hacacao crop), (2) grassland (12?ha), and (3) urban area (3?ha). A total of 67 nests were found, representing five stingless bee species, Tetragonisca angustula angustula (Lepeletier), Trigona fulviventris (Guérin), Scaptotrigona mexicana (Guérin), Scaptotrigona pectoralis (Dalla Torre), and Oxytrigona mediorufa (Cockerell). The most abundant stingless bee in each site was T. angustula angustula (>50%). The primary tree species used by the bees were Ficus spp. (Moraceae, 37.8%) and Cordia alliodora (Boraginaceae, 13.5%). The nest entrance height of T. angustula angustula (96?±?19?cm) was different than the other species, and this bee was the only one that used all different nesting sites. Volatiles analyzed by gas chromatography from pollen collected by the stingless bees differed between bee species, but were highly similar in respect to the fragrances of the pollen collected by the same species at any site. Our data indicate that T. angustula angustula experienced low heterospecific and high intraspecific foraging overlap especially in the urban site. We observed cluster spatial distribution in grassland and in agroforestry sites. In the urban site, T. angustula angustula presented random distribution tended to disperse. Trigona fulviventris was the only overdispersed and solitary species.     

Social Modulation of Stress Reactivity and Learning in Young Worker Honey Bees

Alarm pheromone and its major component isopentylacetate induce stress-like responses in forager honey bees, impairing their ability to associate odors with a food reward. We investigated whether isopentylacetate exposure decreases appetitive learning also in young worker bees. While isopentylacetate-induced learning deficits were observed in guards and foragers collected from a queen-right colony, learning impairments resulting from exposure to this pheromone could not be detected in bees cleaning cells. As cell cleaners are generally among the youngest workers in the colony, effects of isopentylacetate on learning behavior were examined further using bees of known age. Adult workers were maintained under laboratory conditions from the time of adult emergence. Fifty percent of the bees were exposed to queen mandibular pheromone during this period, whereas control bees were not exposed to this pheromone. Isopentylacetate-induced learning impairments were apparent in young (less than one week old) controls, but not in bees of the same age exposed to queen mandibular pheromone. This study reveals young worker bees can exhibit a stress-like response to alarm pheromone, but isopentylacetate-induced learning impairments in young bees are suppressed by queen mandibular pheromone. While isopentylacetate exposure reduced responses during associative learning (acquisition), it did not affect one-hour memory retrieval.     

Social Reinforcement Delays in Free-Flying Honey Bees (Apis mellifera L.)

Free-flying honey bees (Apis mellifera L.) reactions were observed when presented with varying schedules of post-reinforcement delays of 0 s, 300 s, or 600 s. We measured inter-visit-interval, response length, inter-response-time, and response rate. Honey bees exposed to these post-reinforcement delay intervals exhibit one of several patterns compared to groups not encountering delays, and had longer inter-visit-intervals. We observed no group differences in inter-response time. Honey bees with higher response rates tended to not finish the experiment. The removal of the delay intervals increased response rates for those subjects that completed the trials.     

Ecology and Evolution of Social Organization in Arctic Sandpipers

A comparative analysis of sandpiper social systems on arcticand subarctic breeding grounds (24 species in the family Scolopacidae,subfamily Calidridinae) shows four major patterns. In a majorityof the species (15), populations are dispersed through a stronglydeveloped territorial system, with strong monogamous pair bondsand only minor yearly fluctuations in numbers. The second patternis seen in three species in which the female of a pair may laytwo sets of eggs in quick succession, one for each member ofthe pair to incubate. This opens opportunities for facultativepolygyny or polyandry (‘serial polygamy’) and forthe evolutionary weakening of the strong pair bond seen in thefirst pattern. The third and fourth patterns are those of polygyny(three species) and promiscuity (three species). These six speciesshow clumped dispersions; their year-to-year fluctuations tendto be strong; the males defend compressible, often small, territories;and high densities can occur locally. It is suggested that thepattern of overdispersion and monogamy represents a conservativemode of adapting to high-latitude environments, while the patternof clumped dispersion with polygyny or promiscuity representsan opportunistic mode in that the birds are concentrated intobreeding areas where and when weather, food, and/or some otherenvironmental factors are particularly favorable. Apparentlyfalling evolutionarily between these two basic patterns areseveral species conservative in their life-styles, but polygamousat least occasionally and showing some features of opportunism.There is thus a striking diversity of social systems in calidridinesandpipers, that is, in the styles of habitat exploitation theyhave evolved in the arctic and subarctic habitats to which theirbreeding is confined. A graphic model suggesting paths of evolutionarydevelopment and of interplay among factors considered criticalin the evolution of these systems is proposed.     

On the Relationship of Social Evolution and Ecology in Ungulates

Much of the social behavior and organization of ungulates canbe related to ecological parameters such as fiber content offorage, plant productivity, plant biomass, plant species diversity,productivity gradients, temporal and spatial fluctuations inproductivity, habitat stability, food dispersion, three-dimensionalstructure of habitat, colonization, and predator density anddiversity. These ecological variables can be linked via individualnatural selection with the species' anti-predator strategies,emphasis on different channels of communication, relative frequencyof damaging and non-damaging overt aggression, gregariousnessand group structure, juvenile dispersal, home-range traditions,monogamy and polygamy, sexual dimorphism, territoriality, hierarchicalrank structure, and plasticity of social structures. The ecologicalvariables have primary manifestations which are behavior orwhich affect behavior, as well as secondary manifestations affectingbehavior. There are logical links between the hypothesis linkingecology and behavior discussed here with some principles frombioenergetics, zoogeography, and paleontology. Although linksdo exist between ecology and behavior, they nevertheless representdistinct realms of natural selection in which social behaviorappears as the more conservative element. The theoretical basisfor this is discussed.     

Bees Scavenge Airborne Bacteria

Abstract An air conditioned wind tunnel system was designed, fabricated, and tested to determine whether tethered bees scavenge microbeads or Bacillus subtilis var. niger spores from aerosols. Tests showed that microbeads and spores were scavenged by bumblebees and honeybees, respectively. Five independent variables and their interactions were used in a stepwise multiple regression. Two of them, the cube root of the electrostatic charge on the honeybee and the dose of the spore aerosol, accounted for most of the statistically significant fit to the model's two dependent variables: the percentage of the dose adsorbed by honeybees and the number of spores adsorbed by the same bees. Both dependent variables increased directly so that an increase in electrostatic charge on the bee (i.e., cube root 32 pC) resulted in an increase (i.e., approximately 1%) in the spore dose adsorbed and the number of spores adsorbed by the bees. It was theorized that the spores were in an adsorption/desorption equilibrium that responded to the concentration ``pressure' of the spore aerosol. Further, the charge on the bee affected the adsorption force on the bee's surface, as well as increasing the effective aerosol volume accessible for the bee's scavenging. In short, relating these findings to bees scavenging bacteria from the ambient atmosphere, it appears that the spore exposure (where exposure means the product of the ambient concentration, the time the bee is exposed, and air volume through which the bee flies) controls the number of spores adsorbed by a bee, and the static charge on the bee controls the adsorption/desorption equilibrium and presumably the scavenging volume. Received: 22 November 1999; Accepted: 21 January 2000; Online Publication: 29 May 2000