Stingless Bee Tetragonisca Angustula Research Articles

Toxicity of botanical insecticides on the stingless bee Tetragonisca angustula

This study aimed to investigate the toxicity of botanical insecticides on the stingless bee Tetragonisca angustula (Apidae: Meliponini). Bioassays evaluated the effects of essential oils (EO) of Allium sativum (Amaryllidaceae), Eucalyptus citriodora (Myrtaceae), and commercial oil (CO) of Azadirachta indica (Meliaceae), in addition to ethanolic extracts (EE) of Piper nigrum (Piperaceae), and Eugenia caryophyllata (Myrtaceae). It was also assessed the effect of Surfactant addition to essential oils. The probit analysis was used to determine LC50 and LC90. Results showed essential oil of E. citriodora at 1% v/v was toxic to T. angustula, with mean mortalities of 42.00 and 46.00% at 96 hours and survival times of 107.52 and 105.60 hours for contact and ingestion, respectively. Ethanolic extracts of P. nigrum and E. caryophyllata caused 100% mortality within 24 hours through ingestion but were less toxic through contact. Surfactants increased mortality caused by the essential oil of E. citriodora from 47.67 to 93.33% and the commercial oil of A. indica from 38.00 to 100%. Essential oil of E. citriodora had the lowest LC50 and LC90 (0.075 and 1.45% v/v), indicating high toxicity to T. angustula. Ethanolic extracts of P. nigrum and E. caryophyllata had higher LC50 and LC90 values, showing lower toxicity. In conclusion, the oils of A. indica and E. citriodora and ethanolic extracts of P. nigrum and E. caryophyllata are toxic to stingless bee T. angustula.

Floral biology and flower visitors of cocoa (Theobroma cacao L.) in the upper Magdalena Valley, Colombia

Cocoa (Theobroma cacao L.) is an important crop, but yield is generally low. Improving yield requires detailed understanding of the reproductive ecology, especially the pollination system and factors determining pollination success, such as proximity to natural areas. Since the 1940s biting midges have been proposed as the pollinators of cocoa flowers but this idea has recently been questioned in various studies. We observed cocoa flowers and their visitors during anthesis, we compare cocoa flower visitors during the day and night and also in plantations connected and disconnected to natural forests. Observations of flowers during anthesis revealed that cocoa flowers are protandrous, open at night, persist for three days and are receptive only during the day. A diversity of insects visited flowers throughout 24 h. In general, insect visitors were more diverse during the day and in plantations connected to forests compared to those not connected to forests. Fifty five percent of the total insect species visited the cocoa flowers at night, all insect species visited cocoa flowers in plantations connected to natural forests and 62.5 % of those visited cocoa flowers in plantations disconnected with forests. Hymenoptera and Diptera were the main visitors and a total of eleven insect species carried cocoa pollen grains. Among those, two species of biting midges (Ceratopogonidae flies) and two species of stingless bees (Meliponini bees) were the most common. While biting midges were the most common visitors, the stingless bee Tetragonisca angustula carried large cocoa pollen loads and interacted with both the male and female parts of the flower. Ants also visited cocoa flowers, mainly at night. The most common visitors of cocoa flowers in cocoa plantations in the upper Magdalena Valley in Colombia are diurnal biting midges and stingless bees, but also nocturnal ants, suggesting that the pollination system of cocoa flowers may be locally less specialized than previously thought. Future research should investigate the effectiveness of various insect groups as pollinators.

Route of exposure to veterinary products in bees: Unraveling pasture's impact on avermectin exposure and tolerance in stingless bees.

Deforestation rapidly increases in tropical regions, primarily driven by converting natural habitats into pastures for extensive cattle ranching. This landscape transformation, coupled with pesticide use, are key drivers of bee population decline. Here, we investigate the impact of pasture-dominated landscapes on colony performance, pesticide exposure, and insecticide sensitivity of the stingless bee Tetragonisca angustula. We monitored 16 colonies located in landscapes with varying proportions of pasture. We collected bee bread for pesticide and palynological analysis. We found a positive correlation between pollen diversity and colony growth, with no effect of the proportion of pasture in the landscape. In contrast, we detected prevalent and hazardous concentrations of the insecticide abamectin (9.6-1,856 µg/kg) in bee bread, which significantly increased with a higher proportion of pasture. Despite the abamectin exposure, the bee colonies displayed no adverse effects on their growth, indicating a potential tolerance response. Further investigations revealed that bees from sites with higher proportions of pasture showed significantly reduced mortality when exposed to a lethal concentration of abamectin (0.021 µg/µL) after 48 h. Since abamectin is scarcely used in the study area, we designed an experiment to track ivermectin, a closely related antiparasitic drug used in cattle. Our findings uncovered a new exposure route of bees to pesticides, wherein ivermectin excreted by cattle is absorbed and biotransformed into abamectin within flowering plants in the pastures. These results highlight that unexplained exposure routes of bees to pesticides remain to be described while also revealing that bees adapt to changing landscapes.

Residual determination and acute toxicity of the neonicotinoid clothianidin in the neotropical stingless bee Tetragonisca angustula Latreille, 1811 (Apidae: Meliponini)

Bees play a crucial role as natural pollinators, ensuring the maintenance and stability of the world’s biodiversity and agricultural crops. Native bees in neotropical regions belong to the Meliponini tribe, a larger group that differs significantly in behavior and biology from honeybees (e.g., Apis mellifera) and solitary bees (e.g., Osmia spp.). Hence, the exposure and effects of pesticides is also likely to vary among these different species. The aim of this study was to develop an analytical method to determine the presence of the neonicotinoid clothianidin in the Brazilian native stingless bee Tetragonisca angustula (local common name: Jataí). The method used for the chemical analysis involved a QuEChERS technique combined with UHPLC-MS/MS analysis. The developed method was subsequently used to analyze collected field samples. In addition, the acute toxicity of the pesticide to T. angustula was evaluated in a laboratory bioassay evaluating both lethal and sublethal endpoints. The analytical method was successfully developed with detection and quantification limits of 1.55 and 5 μg L−1, respectively, along with a linear range of 1–5 ng mL−1. Clothianidin was detected in environmental samples (9.2–32.9 ng g−1), and the exposure experiments demonstrated acute oral toxicity to adults of T. angustula, (24 h-LD50 of 0.16 ng a.i./bee), as well as no significative interference in acetylcholinesterase activity. Considering the obtained toxicity endpoints for T. angustula and those reported in the literature for other bee species, this study revealed that T. angustula is more (lethally) sensitive to clothianidin than other bee species, including those commonly used in environmental risk assessment studies. This thus also supports the call for using native test species in (regional) risk assessment evaluations.

Weeds as an essential component of sustainable meliponiculture practices in organic agroecosystem

Knowledge of bee flora is key information for sustainable meliponiculture practices. Aiming to stablish the plant species used by the stingless bee Tetragonisca angustula used as food sources during the year in an organic agroecosystem, this study identified the pollen grains in the pollen loads of worker bees. The pollen load of bees returning to hives was collected bi-monthly for one year, summing 240 pollen loads analyzed by optical microscopy. We found 76 pollen types in the pollen loads, of which 60% were of weeds. The plants most frequently identified in the pollen loads were: Alchornea, Arracacia xanthorrhiza, Baccharis, Bidens pilosa, Brassica juncea, Brassica oleracea, Byrsonima sp., Cecropia, Chamaecrista, Citrus sp., Crotalaria sp., Croton, Datura, Eucalyptus, Hyptis, Lippia alba, Mangifera indica, Melastomataceae sp., Momordica charantia, Myrsine, Pereskia aculeata, Persea americana, Piptadenia, Pisum sativum, Plinia peruviana, Pluchea, Poaceae, Prunus persica, Psidium guajava, Raphanus sativus, Rubus urticifolius, Schefflera, and Schinus. Bees foraged mostly on weeds, especially during winter and autumn, and so the presence of weeds can be very beneficial to meliponiculture practices. The by-products of meliponiculture in agroecosystems are derived from diversified botanical sources, that is, wild honey of good quality because it is from an organic system.

Abamectin and difenoconazole monitoring in strawberry flowers and pollen sampled from Tetragonisca angustula (Latreille) (Hymenoptera: Apidae) hives located in crop vicinities

The increase in agricultural productivity associated with the emergence and the extensive use of pesticides is undeniable. However, strong evidence indicates that this continuous demand is causing serious environmental impacts and bringing toxic effects to associated biota as pollinating insects. The present work aims the determination of the insecticide abamectin (ABA) and the fungicide difenoconazole (DIF) in strawberry flowers (Fragaria x ananassa DUCH.) and pollen sampled from beehives of the stingless bee Tetragonisca angustula Latreille (Hymenoptera: Apidae) located nearby strawberry fields. For analysis, QuEChERS method was optimized, and the analytical performance of those two pesticides was verified. Then, the method was applied to strawberry flowers and the pollen was sampled during three field campaigns. While abamectin was not detected, the systemic fungicide difenoconazole was determined in almost all flowers and pollen samples, demonstrating the major persistence of this pesticide in investigated matrices. The results were then discussed about the difenoconazole application rate and transport to colonies to estimate a preliminary environmental risk assessment for stingless native bees. All calculations were proceeded considering exposure rates and toxicity data from the literature, adapted from Apis mellifera studies. In this sense, the determination, application, and discussion about risk assessment figure out as an important tool to the knowledge about the preliminary risks of native bees exposed to pesticides.

Comparison of the Sensitivity of Tetragonisca angustula (Apidae-Meliponini) and Apis mellifera (Apidae-Apini) to Three Insecticides (Malathion, Imidacloprid, and Fipronil) Used in Costa Rica.

The decline of insect pollinators is a significant concern within the current biodiversity crisis. The paradox between the benefits that these animals represent to humans and the evidence of human activities driving their extinction calls for the urgent protection of bees. To address the role of chemical pollution in this scenario, we assessed the acute toxicity as well as four biomarker responses (cholinesterase [ChE], glutathione S-transferase, catalase, and lipid peroxidation [LPO]) elicited by dietary 24-h exposure to three insecticides (malathion, imidacloprid, and fipronil) on the stingless neotropical bee Tetragonisca angustula and the honeybee Apis mellifera. Malathion was the most toxic substance to both species, with 48-h median lethal doses (LD50s) of 0.25 ng/bee to A. mellifera and 0.02 ng/bee to T. angustula. Fipronil was also highly toxic and presented a similar toxicity to both species, with 48-h LD50s of 0.5 ng/bee (A. mellifera) and 0.4 ng/bee (T. angustula). Imidacloprid had the lowest acute toxicity with a 48-h LD50 of 29 ng/bee for A. mellifera, whereas T. angustula tolerated exposure higher than 35 ng/bee. Apparent biomarker responses were observed in bees of both species that survived exposure to higher concentrations of malathion (ChE inhibition) and fipronil (increased LPO). Our results suggest that specific sensitivity to insecticides varies greatly among compounds and pollinator species, but the use of different representative species can facilitate the prioritization of substances regarding their risk to pollinators. Further research is necessary to better characterize the risk that pesticides represent in neotropical agricultural landscapes. Environ Toxicol Chem 2023;42:1022-1031. © 2023 SETAC.

Distribution pattern of arthropods on the leaf surfaces of Acacia auriculiformis saplings.

Acacia auriculiformis A. Cunn. Ex Benth. (Fabaceae), a non-native pioneer species in Brazil with fast growth and rusticity, is used in restoration programs. Our goal was to assess during a 24-month survey the pattern of arthropods (phytophagous insects, bees, spiders, and predator insects) on the leaf surfaces of A. auriculiformis saplings. Fourteen species of phytophagous, two of bees and eleven of predators were most abundant on the adaxial surface. The values of the ecological indexes (abundance, diversity, and species richness) and the rarefaction, and k-dominance curves of phytophagous, bees and arthropod predators were highest on the adaxial leaf surface of A. auriculiformis. The k-dominance and abundance of Aleyrodidae (Hemiptera) (both leaf surfaces), the native stingless bee Tetragonisca angustula Latreille (Hymenoptera: Apidae) (both leaf surfaces) and the ant Brachymyrmex sp. (adaxial surface) and Pheidole sp. (Hymenoptera: Formicidae) (abaxial surface) were the highest between the taxonomic groups of phytophagous, bees, and predators, respectively on A. auriculiformis saplings. The ecological indexes and rarefaction, abundance, and k-dominance curves of phytophagous insects, bees, and predators were highest on the adaxial leaf surface. The preference of phytophagous insects for the adaxial leaf surface is probably due to the lower effort required to move on this surface. Understanding the arthropod preferences between leaf surfaces may help to develop sampling and pest management plans for the most abundant phytophagous insects on A. auriculiformis saplings. Also, knowledge on the preference pattern of bees and predators may be used to favour their conservation.

Toxicological evaluation of different pesticides in Tetragonisca angustula Latreille (Hymenoptera, Apidae)

The stingless bee Tetragonisca angustula is an important pollinator of different agricultural and native crops. This study evaluated changes in the relative activity of esterases and critical electrolyte concentration in brain cells after exposure to pesticides malathion and thiamethoxam. Lethal concentration 50% showed greater toxicity of thiamethoxam in relation to malathion. Esterases EST-3 and EST-4 (carboxylesterase) were partially inhibited after contamination by contact and ingestion of malathion and contamination by contact with thiamethoxam, suggesting participation of these esterases in the metabolization of these compounds. The lowest critical electrolyte concentration (CEC) was found after contamination by malathion ingestion (0.15 M), indicating changes in gene expression. The alterations observed in the intensity of EST-3 and EST-4 and the chromatin structure indicate that pesticides can act in gene expression and be used as biomarkers of contaminant residues. Furthermore, knowing the susceptibility of T. angustula bees to pesticides, it would be possible to use this species for biomonitoring environmental quality in preserved areas and agroecosystems.

Impacts of a tailing dam break on the contamination of pollen and honey from the stingless bee Tetragonisca angustula (Apidae: Trigonini)

Metal and metalloid pollution are one of the main negative impacts of mining activities. Furthermore, the mining wastes are often stored in tailing dams, which are prone to failures and even total collapse. The Fundão tailing dam collapse in Brazil in 2015 flooded large areas of river floodplains below the dam. We analyzed the effect of the tailing deposition from the dam disaster on metal/metalloid levels in honey and pollen samples from the stingless bee Tetragonisca angustula. Pollen and honey samples were taken from the initial stretch of the impacted areas, as well as adjacent control areas and an additional external control area. In total, we analyzed 55 pollen samples and 53 honey samples, which were collected directly from the honey and pollen combs stored within the hives. The samples were wet acid digested in a microwave oven and the concentrations of the elements were determined by ICP-OES and ICP-MS. The metal/metalloid contents in honey and pollen samples were compared between the impacted and the non-impacted points. We found significantly higher concentrations of As, Ba, Cr, Mn, Ni and Zn, in honey and pollen samples, from some impacted points compared to the reference non-impacted ones. However, most concentrations we found were similar to those found in other works, including areas with mining activity in the Iron Quadrangle (Minas Gerais, Brazil). These results suggest that the tailing dram break, followed by deposition of the dam waste, contributed to a high concentration of some elements found in the pollen and honey samples at our study site.

Gene expression and epigenetics reveal species-specific mechanisms acting upon common molecular pathways in the evolution of task division in bees

A striking feature of advanced insect societies is the existence of workers that forgo reproduction. Two broad types of workers exist in eusocial bees: nurses who care for their young siblings and the queen, and foragers who guard the nest and forage for food. Comparisons between these two worker subcastes have been performed in honeybees, but data from other bees are scarce. To understand whether similar molecular mechanisms are involved in nurse-forager differences across distinct species, we compared gene expression and DNA methylation profiles between nurses and foragers of the buff-tailed bumblebee Bombus terrestris and the stingless bee Tetragonisca angustula. These datasets were then compared to previous findings from honeybees. Our analyses revealed that although the expression pattern of genes is often species-specific, many of the biological processes and molecular pathways involved are common. Moreover, the correlation between gene expression and DNA methylation was dependent on the nucleotide context, and non-CG methylation appeared to be a relevant factor in the behavioral changes of the workers. In summary, task specialization in worker bees is characterized by a plastic and mosaic molecular pattern, with species-specific mechanisms acting upon broad common pathways across species.

Magnetosensitivity in the Stingless Bee Tetragonisca angustula: Magnetic Inclination Can Alter the Choice of the Flying Departure Angle From the Nest.

It is known that animals are sensitive to the geomagnetic field. In the case of insects, magnetoreception has been reported in several ant species and in some bees and wasps. One study showed that the stingless bee Tetragonisca angustula is able to sense the modification of the magnetic field inclination. The aim of the present manuscript is to continue that study in T. angustula, analyzing the nest arrival and departure angles in the presence of magnetic fields generated by magnets. The bees flying to and from the nest were recorded and the flying trajectories were obtained by analyzing the video frame by frame. The magnetic field was generated by 6, 9, or 12 magnets contained inside an Eppendorf tube and fixed near the nest. Our results show that T. angustula bees are sensitive to magnetic fields because the departure angles are influenced by the magnets. It was observed that these bees are sensitive to the polarization of the magnetic field vector that influences the choice of flying up or down, and this sensitivity has a window until about 80 μT (about four times the local geomagnetic field), with the magnetic field information for higher magnetic field intensities being ignored by the bees. Bioelectromagnetics. 2021;42:51-59. © 2020 Bioelectromagnetics Society.

Chemosensory reception in the stingless bee Tetragonisca angustula

In stingless bees, unlike honey bees, the relationship between chemosensory abilities and colony labor division has been poorly studied. Here we examined odor reception and gustatory responsiveness of the stingless bee Tetragonisca angustula focusing on workers, whose are involved in different tasks. Using the proboscis extension response, we studied sucrose response thresholds (SRTs) of foragers and guards. Peripheral responses to odors at the antennae were recorded by electroantennography (EAG). Additionally, we quantified and described the number and type of sensilla present on the antennae using scanning electron microscopy. Foragers’ SRTs changed according to the resource collected: nonpollen foragers showed higher SRTs than pollen foragers and guards, that showed similar sucrose responsiveness. EAG signal strength of both foragers and guards increased with increasing odor concentration. Interestingly, guard bees showed the highest response to citral, an odor that triggers defensive behavior in T. angustula. Type and number of sensilla present in the antennae of guards and foragers were similar. Our results suggest that differences found in chemosensory responses among worker subcastes are task dependent.

Bee colony losses in Brazil: a 5-year online survey

In 2014, an online survey was launched to assess impacts of bee losses in Brazil (honeybees, stingless bees, and solitary bees). Events from January 2013 to December 2017 were collected on a website http://www.semabelhasemalimento.com.br/beealert as well as in apps for smartphones and tablets. In total, 322 post-confirmed qualified reports (287 for honeybee, 33 for stingless bee, 2 for solitary bee) were included in our analyses. Overall, 19,296 of 37,453 colonies and nests were lost (estimated > 1 billion bees). Losses were highest for Africanized honeybees (Apis mellifera), followed by stingless bee Tetragonisca angustula. Honeybee 95% confidence intervals (CI) for loss rates on the basis of year, 5-year interval, regions, and operation sizes were estimated using a generalized linear model (GLM) for total loss (TL) and a Wald method for average losses (AL). Other species losses were mentioned in the text. Based on information from respondents, pesticide exposures were suspected as the main cause of nest and colony losses. In Sao Paulo State, which accounted for 45.7% of total reports, neonicotinoids and fipronil led pesticide are listed in 55.9% of reports (fipronil, clothianidin, imidacloprid, and thiamethoxam are widely used in sugar cane plantations and orange groves in this state).

Changing of the guard: mixed specialization and flexibility in nest defense (Tetragonisca angustula)

AbstractTask allocation is a central challenge of collective behavior in a variety of group-living species, and this is particularly the case for the allocation of social insect workers for group defense. In social insects, both benefits and considerable costs are associated with the production of specialized soldiers. We asked whether colonies mitigate costs of production of specialized soldiers by simultaneously employing behavioral flexibility in nonspecialist workers that can augment defense capabilities at short time scales. We studied colonies of the stingless bee Tetragonisca angustula, a species that has 2 discrete nest-guarding tasks typically performed by majors: hovering guarding and standing guarding. Majors showed age polyethism across nest-guarding tasks, first hovering and then changing to the task of standing guarding after 1 week. Colonies were also able to reassign minors to guarding tasks when majors were experimentally removed. Replacement guards persisted in nest defense tasks until colonies produced enough majors to return to their initial state. Tetragonisca angustula colonies thus employed a coordinated set of specialization strategies in nest defense: morphologically specialized soldiers, age polyethism among soldiers within specific guarding tasks, and rapid flexible reallocation of nonspecialists to guarding during soldier loss. This mixed strategy achieves the benefits of a highly specialized defensive force while maintaining the potential for rapid reinforcement when soldiers are lost or colonies face unexpectedly intense attack.

The impact of four widely used neonicotinoid insecticides on Tetragonisca angustula (Latreille) (Hymenoptera: Apidae)

Application of neonicotinoid insecticides on crops can reduce the pollination services and population levels of the stingless bee Tetragonisca angustula (Latreille) (Hymenoptera: Apidae) in Neotropical agroecosystems. However, the impact of these insecticides on this bee has not been fully investigated. This study assessed the susceptibility levels of T. angustula to four neonicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid and thiamethoxam), widely used to manage pests on different crops, and their effects on locomotion of the bee. Neonicotinoids with the cyano radical caused lower bee mortality (assessed by mean lethal concentration, LC50), while those compounds with the nitro radical were highly harmful to T. angustula. Locomotion activity was strongly impaired in bees treated with thiacloprid and imidacloprid, while acetamiprid did not affect the locomotion activity, which was similar to the control. Application of thiamethoxam caused hyperactivity, as observed by increases of ∼4.5 and 5.0-fold in mean speed and distance traveled, respectively. These results suggest that applications of neonicotinoid insecticides can negatively affect the pollination activity of T. angustula. These results can also help to develop strategies to conserve these pollinators in agroecosystems.

Phylogenetic analyses of antibiotic-producing Streptomyces sp. isolates obtained from the stingless-bee Tetragonisca angustula (Apidae: Meliponini).

Many insects have been associated with actinobacteria in protective symbiosis where antimicrobial metabolites inhibit host pathogens. However, the microbiota of neotropical insects such as the stingless-bee Tetragonisca angustula is poorly explored. T. angustula is a meliponid bee widely distributed in Latin America, its honey is traditionally exploited because of its ethno-pharmacological properties and its antimicrobial activity has been demonstrated. Also, the well-structured nest of this species allows exploration of the microbiota of its different components. Even though Streptomyces spp. have been cultured from stingless-bees, little is known about their role in this insect-microbe relationship. In this study, we examined the association between culturable actinobacteria and T. angustula, and evaluated the isolates' potential as antimicrobial producers. We isolated 51 actinobacteria from adult bees and different substrates of the hive of T. angustula (pollen and honey storage, garbage pellets and cerumen). We then performed a 16S rRNA phylogenetic analysis that clusters the bacteria to previously described lineages of host-associated Streptomyces. In addition, all the isolates were classified according to their antibacterial activity against human pathogens, measured by a growth inhibition test based on diffusion in agar. More than 50 % of our isolates exhibit antimicrobial activity, mainly to Gram-positive bacteria and fungi and only two against Gram-negative bacteria. Additionally, we obtained electron micrographs of adult bees with what appears to be patches of hyphae with Streptomyces-like cell morphology on their body surface. Our results suggest that T. angustula possibly uptakes and transfers actinobacteria from the environment, acting as vectors for these potentially beneficial organisms. This research provides new insights regarding the microbiota associated with T. angustula and justify future studies exploring the full diversity of the microbial community associated with the hive and the possible exchange of microbes with the crops they pollinate.

Ambush Predation of Stingless Bees (Tetragonisca angustula) by the Solitary-Foraging Ant Ectatomma tuberculatum

Social insect colonies are high-value foraging targets for insectivores, prompting the evolution of complex colony defensive adaptations as well as specialized foraging tactics in social insect predators. Predatory ants that forage on other social insects employ a diverse range of behaviors targeted at specific prey species. Here, we describe a solitary foraging strategy of the ant Ectatomma tuberculatum, on nest guards of the stingless bee Tetragonisca angustula. We observed multiple instances of E. tuberculatum ambushing and successfully capturing the hovering and standing guards of T. angustula near nest entrances. The unique hovering behavior of the guard caste of this bee species, an adaptation to frequent cleptoparasitism by other stingless bees, may make these guards particularly vulnerable to ground-based, ambush attacks by E. tuberculatum. Likewise, the behavior of the foraging ants appears to adaptively exploit the defensive formations and activity patterns of these bees. These observations suggest an adaptive and targeted predatory strategy aimed at gathering external guard bees as prey from these heavily fortified nests.

Potential pollinators of understory populations of <i>Symphonia globulifera</i> in the Neotropics.

One difference between the forest canopy and the understory is that animals pollinate the majority of understory species in the tropical wet forest. Pollinators active in the understory are also different from those in the forest canopy and are adapted to the mesic conditions underneath the canopy. We used video cameras to observe flowers of understory Symphonia globulifera (Clusiaceae) in tropical wet forests of Costa Rica. We quantified the timing, frequency and behaviour of flower visitors to explore their potential contribution to pollination. A total of 82 flower visits were observed during 105 h of observations. Flowers were visited by ten insect species and one hummingbird species; the most active time period was between 1200-1700 h followed by the time between 0500-1000 h. The time period with fewer visitors was 1700-2200 h, during this period we observed flowers visited in multiple instances by a bushcricket (Tettigoniidae). The most frequent flower visitors were the stingless bee Tetragonisca angustula and the hummingbird Phaethornis longirostris; both came in contact with anther and stigma during visits. We observed different flower visitors from those reported for canopy populations of S. globulifera. Insects predominated, in contrast to observations in canopy populations of S. globulifera, wherein perching birds predominated. We also documented the consumption of pollen by visiting insects. These findings highlight differences in flower visitors between the forest canopy and the understory for the same tree species and contribute to better understanding of the pollination ecology of understory tropical wet forest species.

Characterization of cuticular hydrocarbons according to colony duties in the stingless bee Tetragonisca angustula

In social insects, task-related recognition plays an important role in the coordination and cohesion between members of the colony. Tetragonisca angustula is an eusocial stingless bee that presents a sophisticated system of defense involving two complementary groups of guards: hovering and standing guards. We identified, quantified, and compared the cuticular compounds of worker bees captured within the nest, and bees performing tasks outside: foragers and guards. In addition to cuticular hydrocarbons (CHCs), we identified abundant di- and triterpenes. Among the CHCs, we found a mixture of n-alkanes, methyl-branched alkanes, alkenes, and alkadienes. Significant differences in the relative abundance of CHCs between behavioral groups were found. Particularly, guards present high amounts of branched alkanes relative to nest bees and foragers. Differential CHC profiles associated with behavioral groups could imply a mechanism for caste recognition.