Search

Based on microsatellite markers and non-lethal sampling of orchid bee males, we assessed the genetic diversity and population structure of three species, Euglossa pleosticta, Euglossa imperialis, and Eulaema nigrita, collected from forest remnants in the Brazilian savanna biome. Among these species, El. nigrita has being acknowledged as more tolerant to savanic areas, since it is more frequently found in these habitats than the other two species. Thus, we hypothesized that species more associated with forest areas would show lower levels of genetic diversity and higher levels of population structure, since open areas could represent a barrier to the movement of these species. We observed lower levels of genetic diversity (HE) in the species highly associated with forest areas (Eg. pleosticta, HE = 0.66; Eg. imperialis, HE = 0.44) compared to El. nigrita (HE = 0.81). Concerning the genetic structure, it was only remarkable among samples of Eg. pleosticta, a species strongly associated with the forest remnants. Despite the documented dispersal capacity of euglossine bees, maintenance of the connections among forest areas in this biome seems to be critical for their conservation in the Brazilian savanna.

Euglossa imperialis Cockerell, 1922 has recently been catalogued in the Cerrado of Mato Grosso do Sul, Brazil, andhere we add both new and old data obtained from expeditions conducted in 10 municipalities of Mato Grosso since2002. In this study we record this species for the first time in the wetlands of Cáceres and Barão de Melgaço, as wellas on the northern Pantanal. Further studies are required to examine the variation in the coloration and other characteristicsin E. imperialis populations from the northern and southern floodplains..

Orchid bees (Hymenoptera: Apidae: Euglossini) are a diverse and important group of Neotropical pollinators. Numerous chemicals have been used in sampling orchid bees, and species-specific attraction, particularly of males, to these chemicals is well known. However, there have been few studies that have quantified differences in the species composition of orchid bees attracted to particular chemicals. In this study, we compared the abundance and species composition of orchid bees collected with 4 commonly used attractants: benzyl acetate, eucalyptol (or cineole), eugenol, and methyl salicylate. Eucalyptol collected the greatest abundance and species richness of orchid bees. Indicator species analysis revealed that 3 species, Euglossa imperialis Cockerell, Euglossa obtusa Dressler, and Eufriesea mexicana (Mocsary), were significantly associated with eucalyptol, and 1, Eulaema marcii Nemesio, with benzyl acetate. The multi-response permutation procedure revealed relatively large differences in speci...

Secondary sexual traits may convey reliable information about males’ ability to resist pathogens and that females may prefer those traits because their genes for resistance would be passed on to their offspring. In many insect species, large males have high mating success and can canalize more resources to the immune function than smaller males. In other species, males use pheromones to identify and attract conspecific mates, and thus, they might function as an honest indicator of a male's condition. The males of orchid bees do not produce pheromones. They collect and store flower volatiles, which are mixed with the volatile blends from other sources, like fungi, sap and resins. These blends are displayed as perfumes during the courtship. In this study, we explored the relationship between inter‐individual variation in body size and blend composition with the males’ phenoloxidase (PO) content in Euglossa imperialis. PO content is a common measure of insect immune response because melanine, its derived molecule, encapsulates parasites and pathogens. Body size and blend composition were related to bees’ phenolic PO content. The inter‐individual variation in body size and tibial contents could indicate differences among males in their skills to gain access to some compounds. The females may evaluate their potential mates through these compounds because some of them are reliable indicators of the males’ capacity to resist infections and parasites.

Fragmentation of habitat can decrease resource availability and restrict movement among geographic areas. Persistence in fragmented landscapes depends on the maintenance of connectivity among populations, without which genetic diversity may decrease and lead to population declines. Bees are particularly vulnerable to the negative effects of low genetic diversity so it is important to understand patterns of dispersal for native bees living in fragmented areas. I used population genetic techniques to characterize patterns of genetic diversity and dispersal for the orchid bee Euglossa imperialis within and among forest fragments in southern Costa Rica, in which the furthest two fragments were 226 km from one another. In addition, I compared results of population genetic analyses conducted with all bees sampled, and results from analyses conducted with a reduced dataset containing only one individual per full sibling family from each site. For both datasets genetic diversity was low within forest fragments, with expected heterozygosity averaging 0.28 for the full dataset and 0.29 for the dataset containing only one full sibling per site. I found no evidence that deforested areas restricted dispersal; pairwise estimates of genetic differentiation $$F_{\text{ST}}^{\prime }$$ among forest fragments averaged 0.01 for the full dataset, and 0 for the dataset containing only one full sibling per site. Genetic distance among sites within forest fragments was significantly correlated to geographic distance for the full dataset, but there was no significant correlation for the dataset that contained only one individual from each full sibling family. This suggests that family structure can drive results of analyses of genetic structure, although reductions in sample sizes following removal of full siblings may have reduced power to detect genetic structure. Despite no evidence for restricted dispersal, the low genetic diversity found suggests that E. imperialis may be an important candidate for future conservation monitoring.

Visually guided flight control in the rainforest is arguably one of the most complex insect behaviors: illumination varies dramatically depending on location [1], and the densely cluttered environment blocks out most of the sky [2]. What visual information do insects sample for flight control in this habitat? To begin answering this question, we determined the visual fields of the ocelli-thought to play a role in attitude stabilization of some flying insects [3-5]-of an orchid bee, Euglossa imperialis. High-resolution 3D models of the ocellar system from X-ray microtomography were used for optical ray tracing simulations. Surprisingly, these showed that each ocellus possesses two distinct visual fields-a focused monocular visual field suitable for detecting features elevated above the horizon and therefore assisting with flight stabilization [3-5] and, unlike other ocelli investigated to date [4, 6, 7], a large trinocular fronto-dorsal visual field shared by all ocelli. Histological analyses show that photoreceptors have similar orientations within each ocellus and are likely to be sensitive to polarized light, as in some other hymenopterans [7, 8]. We also found that the average receptor orientation is offset between the ocelli, each having different axes of polarization sensitivity relative to the head. Unlike the eyes of any other insect described to date, this ocellar system meets the requirements of a true polarization analyzer [9, 10]. The ocelli of E. imperialis could provide sensitive compass information for navigation in the rainforest and, additionally, provide cues for visual discrimination or flight control.

Bees (Apidae) are flower-visiting insects that possess highly efficient mouthparts for the ingestion of nectar and other sucrose fluids. Their mouthparts are composed of mandibles and a tube-like proboscis. The proboscis forms a food canal, which encompasses a protrusible and hairy tongue to load and imbibe nectar, representing a fluid-feeding technique with a low Reynolds number. The western honey bee, Apis mellifera ligustica, can rhythmically erect the tongue microtrichia to regulate the glossal shape, achieving a tradeoff between nectar intake rate and viscous drag. Neotropical orchid bees (Euglossa imperialis) possess a proboscis longer than the body and combines this lapping-sucking mode of fluid-feeding with suction feeding. This additional technique of nectar uptake may have different biophysics. In order to reveal the effect of special structures of mouthparts in terms of feeding efficiency, we build a temporal model for orchid bees considering fluid transport in multi-states including active suction, tongue protraction and viscous dipping. Our model indicates that the dipping technique employed by honey bees can contribute to more than seven times the volumetric and energetic intake rate at a certain nectar concentration compared with the combined mode used by orchid bees. The high capability of the honey bee's proboscis to ingest nectar may inspire micropumps for transporting viscous liquid with higher efficiency.

The occurrence of Euglossa imperialis Cockerell, 1922 is recorded for the first time in Mato Grosso do Sul, Brazil. This paper extends the distribution of the species by about 800 km west of the São Paulo state, its nearest record.

Male orchid bees (Euglossini) collect volatiles from their environment to concoct species-specific “perfumes”, which are later emitted at mating sites. Intensity, complexity or composition of perfumes may encode age (survival) of a male, but how the individual perfume develops over time needs to be clarified. We investigated chemical changes during storage in leg pockets. We injected a mixture of eight perfume compounds into pockets of Euglossa imperialis and only the two most volatile compounds decreased over 12 days. Using a different approach we found significant shifts in quantities of naturally occurring perfume compounds of Euglossa championi over 10 days, with the strongest decreases (up to 70% peak area) in highly volatile minor compounds, e.g. monoterpenes, and noteworthy increases (up to 40%) in some sesquiterpenoids. Corresponding shifts were observed in legs of dried bees, suggesting that no metabolic activity is required for the observed changes to occur. Our results confirm that male orchid bees are generally good at preserving collected perfumes. However, subtle shifts towards heavier compounds in blends may occur over the lifetime of individual bees, e.g. due to evaporation or in-pocket chemical reaction, with old males acquiring a more pronounced base note in their seasoned perfumes.

Bees are important models to study the physiological role of endocrine cells. These cells produce hormones and may be open or closed cells depending on whether they have direct or indirect contact with the gut lumen, respectively. Food is digested and absorbed in the insect midgut. The objective of this study was to identify endocrine cells in the midgut of bees of different levels of sociability to understand the function of these cells. The midgut of Centris fuscata, Epicharis flava, Euglossa imperialis, Eulaema nigrita, Frieseomelitta varia, Megachile rava, and Melipona quadrifasciata anthidioides (Hymenoptera: Apoidea) was subjected to immunohistochemistry test for FMRF-amide. The midguts of E. imperialis, E. nigrita, and M. rava showed closed FMRFamide-positive endocrine cells, and those of E. flava, F. varia, and M. quadrifasciata anthidioides showed open cells. The greater number of open FMRFamide-positive cells suggest that this peptide probably regulates the synthesis of digestive enzymes without...

We used contrast-optimized micro X-ray computed tomography (mCT) to trace the profiles of the full complement of large ocellar L-neurons in the male orchid bee Euglossa imperialis. We find that most L-neurons collect information from either the dorsal or the ventral retinae in both median and lateral ocelli, with only three neurons associated with the median ocellus having dendritic branches in both dorsal and ventral retina. In the median ocellus, we find also L-neurons that either collect information from the left or the right half of the ocellar plexus and two neurons that have a split dendritic tree in both halves. Fourteen large L-neurons collect information from the median ocellus and six to seven L-neurons from each of the lateral ocelli. The only L-neurons that project to the contralateral protocerebrum are those that have their dendritic branches in the ventral plexi of both median and lateral ocelli. The target areas of dorsal L-neurons from the lateral ocelli include a tract of mechanosensory fibers originating in the antennae. We compare our findings with what is known from the ocellar systems of other insects, make a number of functional inferences and discuss the advantages and disadvantages of mCT scans for the purpose of tracing large neuron profiles.

Os ambientes urbanos têm se tornado refúgio para muitas espécies, entre as quais algumas abelhas da tribo Euglossini. O grupo inclui espécies dotadas de grande capacidade de voo, por isso são consideradas importantes polinizadores neotropicais. São escassas informações sobre Euglossini no Cerrado, são incompletas informações como a distribuição geográfica, quais são endêmicas e quais são cosmopolitas. Assim, este estudo teve como objetivo identificar e analisar a composição de espécies de abelhas da tribo Euglossini ocorrentes em parques urbanos quanto à abundância, riqueza e atratividade através da utilização de iscas odoríferas. Os exemplares de Euglossini foram coletadas mensalmente no período de abril a agosto de 2008, em quatro parques urbanos de Goiânia, Goiás. As abelhas foram amostradas com auxilio de armadilhas de cheiro, expostas das 8 horas às 12 horas, contendo uma das essências: salicilato de metila, acetato de benzila, cineol, vanilina. Foram coletados 147 machos de Euglossini pertencentes a três gêneros e cinco espécies. Houve uma forte dominância de indivíduos de Eulaema nigrita Lepeletier (95,23%), seguida por Euglossa cordata (Linnaeus) (2,72%). O Cineol foi a essência que atraiu a maior abundância de machos e o salicilato de metila apresentou a maior riqueza de espécies atraídas. Este estudo constitui o primeiro registro de ocorrência das espécies Exaerete smaragdina (Guérin) e Euglossa imperialis Cockerell para a região Centro-Oeste e de Euglossa variabilis Friese para o Cerrado. A preservação do conjunto dessas áreas irá manter as populações de abelhas silvestres nestas regiões de importância ecológica, mantendo os serviços de polinização das espécies de plantas. Richness and Abundance of Euglossini Bees (Hymenoptera, Apidae) in Urban Parks in Goiânia, Goiás Abstract. Urban environments have become a refuge for many species, including some bees of the tribe Euglossini. The group includes species with large capacity flight, so they are considered important neotropical pollinators. Euglossini is scarce information about the Cerrado, incomplete information like geographic distribution, which are endemic and which are cosmopolitan. This study aimed to identify and analyze the composition of bee species of the tribe Euglossini occurring in urban parks as to abundance, richness and attractiveness through the use of scent baits. The specimens of Euglossini were collected monthly from April to August 2008 in four urban parks in Goiânia, Goiás. The bees were sampled with the aid of scent traps, exposed from 8 am to 12 noon, containing one of the essences: salicylate methyl, benzyl acetate, cineole, vanillin. We collected 147 male orchid bees belonging to three genera and five species. There was a strong dominance of individuals Eulaema nigrita Lepeletier (95.23%), followed by Euglossa cordata (Linnaeus) (2.72%). The Cineol was the essence that attracted the greatest abundance of males and methyl salicylate had the highest species richness attracted. This study is the first record of species occurrence of Exaerete smaragdina (Guérin) and Euglossa imperialis Cockerell for the Midwest and Euglossa variabilis Friese for the Cerrado. The preservation of all these areas will keep bee populations of wild these regions ecological importance of maintaining the service pollination of plant species.

Euglossini são abelhas típicas de florestas Neotropicais úmidas e poucas espécies ocorrem na caatinga. O rio São Francisco, o único perene do semi-árido brasileiro, é margeado por mata ciliar perenifólia. Esse ambiente oferece recursos florais ao longo do ano. Inventários de Euglossini mostraram que espécies da Floresta Atlântica como Euglossa imperialis Cockerel, E. truncata Moure e Eulaema cingulata Fabricius ocorrem na mata ciliar do rio São Francisco. Estas abelhas são restritas às matas ciliares que funcionam como biocorredores, sendo ausentes em locais onde as matas foram derrubadas. Isto enfatiza a necessidade de proteção das matas ciliares para a manutenção da biodiversidade. Euglossini are typical bees of Neotropical rainforests and only a few species occur in the Caatinga. The São Francisco river, which is the only permanent river in the semi-arid NE-Brazil, is bordered by a gallery forest with evergreen leaves. This environment offers flooral rewards along the year. Surveys of euglossine bees by attracting males to scent baits showed that species of the Atlantic Rainforest like Euglossa imperialis Cockerel, E. truncata Moure and Eulaema cingulata Fabricius occur in the gallery forest of the São Francisco river under the semi-arid climate of the caatinga region. These bees are restricted to the gallery forests which function as bio-corridors, and are absent at places where the forests were cut down. This emphasizes the need to protect the threatened gallery forests to maintain biodiversity.

International audience; AbstractWe evaluate the permeability of three matrices of arboreal crops for the Euglossina bees that inhabit the Brazilian Atlantic rainforest hotspot. The comparisons of occurrences and abundances within three mosaics of forest and extensive arboreal crops (piassava palm, oil palm, and rubber tree) showed that all the matrices were permeable to most orchid bees. The piassava palm was the most permeable, where the spatial distribution of all species of Euglossina did not differ between forest fragments and matrix. The oil palm has shown some loss of permeability to Eulaema atleticana, while the rubber tree crop was not so permeable to El. atleticana and Euglossa imperialis. Euglossa iopoecila was sampled only in the forest fragments. At the present scale of forest cover in the three studied mosaics (10 to 40 %), the arboreal matrices are contributing towards the functional connectivity in the Atlantic Rain Forest at both scales: the landscape mosaic and the Brazilian Atlantic Forest corridor.

SUMMARYThe orchid bee Euglossa imperialis sucks nectars through a slender proboscis. I tested how nectar properties influence this suction pressure and whether ambient air pressure sets the upper limit for suction feeding. Nectar intake rate was measured as a function of sucrose concentration (5-75% w/w),nectar viscosity (2-80 mPa s), and ambient pressure (101-40 kPa). Intake rate declines from about 1.2 μl s-1 to 0.003 μl s-1 as sucrose concentration increases from 15% to 65% sucrose. When sucrose concentration is held at 25% while viscosity increases from 2 to 80 mPa s,intake rate declines. When viscosity is held at 10.2 mPa s (the viscosity of 50% sucrose) while sucrose concentration increases from 5% to 50%, intake rate remains constant. Intake rate was limited by a reduction in ambient pressure at all nectar concentrations. Assuming a rigid proboscis, the Hagen-Poiseuille equation suggests that suction pressure increases with viscosity from 10 kPa at 5% sucrose to 45 kPa at 65% sucrose. However, because intake rate declined by the same fraction under hypobaria (40 kPa) at all sucrose concentrations,the euglossine bee proboscis may be better described as a collapsible tube:expanding or collapsing depending on the flow rate, the pressure gradient along the proboscis, and circumferential forces imposed by the proboscis walls.

Individually marked males of two species of Euglossa were sighted repeatedly and over considerable periods of time (up to 44 days) at artificial fragrance baits exposed on Barro Colorado Island (BCI), Panama. Individuals switched between different bait chemicals that are attractive for the respective species, and no bait preferences or individual bait constancy was observed. GC-MS analyses of 153 males of three species showed that individual hind tibiae contain highly variable quantities of a complex and species-specific blend of fragrance compounds, mainly terpenoids and aromatics. In all three species, frequency distributions of individual quantities were strongly skewed towards individuals with small amounts, and individual amount and complexity were positively correlated. Tibial contents of male Euglossa imperialis that were kept alive in a flight cage for 0, 5, 10, or 15 days showed no qualitative or quantitative change over time, suggesting that the fragrances are very efficiently stored in the hind legs. In Euglossa cognata wing wear, an established age correlate of the species, was positively correlated with individual fragrance quantity. Our results suggest that male euglossines forage continuously for a variety of volatiles, store them, and finally acquire large quantities of a complex and specific fragrance bouquet. Both qualitative and quantitative aspects of individual contents are likely to contain information on male phenotypic and genotypic quality.

This paper reports the results concerning collection of Euglossinae bees in a mangrove ecosystem in Valença(13º22'08"S and 39º04'20"W), Bahia. These samples were made twice a month, for a year. The chemical baits Citronella, Eucalyptol, Eugenol, Metyl Salicylate and Vanillin attracted 1,144 specimens distributed among twelve species and two genera: Eulaema (Lepeletier, 1841) and Euglossa (Latreille, 1802). The predominam bee species was Eulaema nigrita (Lepeletier, 1841) consisting of 49.4% of the collected specimens, followed by Euglossa cordata (Linnaeus, 1758) with 44.88%, Euglossa imperialis (Cockerell, 1922) with 2.4% and Eulaema meriana flavescens (Friese, 1899) with 1.6%. Theothers species, considering sporadic visitors, Euglossa securigera (Dressler, 1982), Euglossa chalybeata (Friese, 1925), Euglossa liopoda (Dressler, 1982), Euglossa gaianii (Dressler, 1982), Euglossa townsendi (Cockerell, 1904), Euglossa truncata (Rebelo & Moure, 1995), Euglossa melanotricha (Moure, 1967) and Euglossa sapphirina (Moure, 1968) represented together only 1.8% of the total sample. The Euglossinae were more active from October to May. Eucalyptol was the most attractive bait, attracting 1,120 specimens. Methyl Salicylate attracted 17 specimens, followed by Eugenol, which attracted 04 specimens and Vanillin, which attracted 03 specimens. Citronella was not an attractive chemical.

SUMMARY To test whether variation in muscle efficiency contributes to thermal stability during flight in the orchid bee, Euglossa imperialis , we measured CO 2 production, heat loss and flight kinematics at different air temperatures ( T a ). We also examined the relationship between wingbeat frequency ( WBF ) and T a in five additional species of orchid bees. Mean thoracic temperature ( T th ) for Eg. imperialis hovering in a screened insectary and in the field was 39.3±0.77°C (mean ± 95% C.I.), and the slope of T th on T a was 0.57. Head and abdominal temperature excess ratios declined with T a , indicating that Eg. imperialis were not increasing heat dissipation from the thorax at high T a . Elevation of T th above T a was correlated with WBF , but T th alone was not. Estimates of heat production from both respirometry and heat loss experiments decreased 33% as T a rose from 24 to 34°C. Mean muscle efficiency over this temperature range was 18% assuming perfect elastic energy storage and 22% assuming zero elastic energy storage. Both efficiency estimates increased significantly as T a rose from 24 to 34°C. In all six species examined, WBF declined significantly with T a . These data indicate that hovering orchid bees regulate heat production through changes in wingbeat kinematics and consequent changes in energy conversion by the flight motor. Temperature-dependent variation in elastic energy storage or muscle contraction efficiency or both may contribute to the observed trends.

Energy flux during nectar feeding is maximized at an intermediate sugar concentration, the value of which depends on the morphology of the feeding apparatus and the modality of fluid feeding. Biomechanical models predict that a shift from capillary-based lapping to suction feeding will lead to a decrease in this optimal sugar concentration. Here, I demonstrate that the four major genera of orchid bees (Apidae: Euglossini) are suction feeders and provide experimental evidence that the feeding optimum for one species, Euglossa imperialis, falls below the optimum for bee taxa that lap.

Pollination deficits in agricultural and natural systems are suggestive of large reductions in pollinator populations. However, actual declines are difficult to demonstrate using census data. Here, we show census data to be misleading because many abundant pollinators exhibit high levels of production of sterile diploid males usually found only in small inbred hymenopteran populations; Euglossa imperialis exhibits high levels of diploid male production induced by low effective population sizes (Ne approximately 15), despite being the most abundant orchid bee in lowland tropical forests in Panama. We caution that although some pollinators appear abundant on the basis of census data, their long-term persistence may be highly tenuous based on genetic evidence. We propose the use of diploid male frequency data as a metric for assessing the sustainability of bee populations.

Male neotropical orchid bees (Euglossini) collect volatile chemicals from orchid flowers and other sources and store them in hind leg cavities. The accumulated fragrance bouquets are later emitted at mating sites. Although most other insects synthesize pheromone blends de novo, specific euglossine perfumes are derived from active choices in a changing fragrance market. Male bees of three species of Euglossa possessed distinctive fragrance phenotypes showing little variation by locality and habitat in mainland Central America. In cage experiments, fragrance choice by male Euglossa imperialis was influenced markedly by a bee's collection history. Collection of a given chemical strongly reduced its attractiveness on subsequent occasions, an effect that was retained over days. Experimentally adding the chemicals directly to bee hind legs produced no effect. We conclude that bees learn and remember chemicals they collect. Innate odor preferences, memory and the avoidance of overcollecting by negative feedback may be the primary mechanisms that ensure unique blends of pheromone analogs in these tropical forest bees.

The male territories of two species of orchid bees, Eulaema meriana and Euglossa imperialis , are described. These territories consist of a perch, where the males display on the trunk of a tree, and a route flown from and back to the perch. Territories are located in treefalls or other large light gaps in tropical forest. The territories of these two species differ in the height of the perch and amount of light reaching it, size of the perch tree, and period of activity. A definition of lek is given. These male euglossines form facultative leks in large treefalls. The relationships between male territories, female foraging ranges, and collection of aromatic material by males are discussed.

Bees in the tribe Euglossini (Apidae) form an important component of the pollinator fauna in lowland, Neotropical forests (Dressler 1982, Janzen 1971, Williams 1982). The community structure and seasonality of male euglossine bees are relatively well known because they can be attracted to chemical baits (Ackerman 1983a, Dodson et al. 1969, Janzen et al. 1982, Pearson & Dressler 1985). The male bees are important pollinators of many orchids (Dressler 1968, Williams 1982) from which they collect fragrant chemicals; these chemicals are also collected from other plants and decaying vegetation (Ackerman 1983b, Dressler 1982). Male bees are known to store collected chemicals in hind tibial organs (Dressler 1982) and, it is presumed, use these chemicals to synthesize sex pheromones (Williams & Whitten 1983). Mating occurs in territories to which males attract female bees (Dodson 1966, Kimsey 1980). Recently, Schemske & Lande (1984) found that captive male Euglossa imperialis show elevated levels of territorial behaviour when provided with cineole, a fragrant chemical that readily attracts male bees, compared to control bees maintained without a chemical source. Although the exact function of the fragrant chemicals is still unknown, these were the first results that clearly implicated fragrance collection in male reproductive behaviour. Schemske & Lande (1984) noted that the male E. imperialis provided with a daily source of cineole actively collected the fragrance only on the first day of the 11 day experiment. One potential explanation for this observation is that males require only one collection of chemical fragrance before establishing territories. Thus, only the youngest bees in the population would be expected

The hypothesis that the understory herbs Costus allenii and C. laevis (Zingiberaceae) have converged in floral characteristics to use the same pollinator was investigated in central Panama. Observations and experiments indicated that these species (1) occupy the same habitats, (2) flower synchronously, (3) are identical in flower color, morphology, and nectar secretion patterns, (4) share the same pollinator, the bee Euglossa imperialis, (5) are self-compatible, but not autogamous, and (6) have strong barriers to hybridization. Both grow in low density along streamsides and produce a single flower per day for an extended period (up to 4 mo). Flower density is depressed through extensive predation by the weevil Cholus cinctus, which damaged 31% of all C. allenii and 60% of all C. laevis inflorescences. Direct observation of foraging bees indicated that individuals regularly visit both plant species. An experimental analysis of interspecific pollen transfer using powdered paint as a marker verified these results; 97% of the flowers checked had received heterospecific visits. The high probability of interspecific pollination did not affect fruiting success. I suggest that low flower density, exaggerated by extreme floral predation, has selected for floral similarity and pollinator sharing in these species. Floral convergence increases effective flower density and nectar supplies, and probably increases the regularity and rate of pollinator visitation.

The nesting biology of Euglossa (Glossura) ignita chlorosoma Cockerell and E. (G.) imperialis Cockerell is described. Both species build nests inhabited by several adult females. The cells are aggregated in a single cluster, similar in arrangement to those of a bumblebee nest. Despite superficial similarities to the social organization of bumblebee colonies, it is concluded that the nonreproductive worker caste essential to sociality is lacking in the species studied and may be absent in all of the Euglossini. Some possible reasons for the absence of sociality are given. The larvae are described and compared with those of the subgenus Euglossa and the closely related genus Euplusia .

The nectar-foraging behavior of male euglossine bees (Hymenoptera: Apidae) was studied at a population of Calathea latifolia (Marantaceae) on Barro Colorado Island, Panama, for two weeks. Several marked males of Exaerete smaragdina and Euglossa imperialis foraged at C. latifolia on a daily basis. Immigration rates were low, and the site fidelity of bees was high. Selection of inflorescences by the marked individuals was not random. The bees learned specific locations of inflorescences at which they consistently foraged and ignored nearby inflorescences. However, not all inflorescences in a bee's repertoire were included in each foraging bout. The sequence of inflorescences visited was not the same within or between days nor were the foraging routes uni-directional. Foraging bouts of both male and female bees did not conform to rigid time schedules. Thus, male euglossine bees are not necessarily as transient and vagabond as previously portrayed. Those males that are site-constant forage in a fashion reminiscent of the traplining behavior once described for females. We propose that euglossine bees change their foraging habits as shifts in resource availability and dispersion occur. EUGLOSSINE BEES ARE IMPORTANT long-distance pollinators of many lowto mid-elevation neotropical plants (Dressler 1968, Dodson 1966, Janzen 1971, Williams and Dodson 1972). Females visit flowers for resin, nectar, and pollen to construct and provision their nests (Michener 1974, Armbruster and Webster 1979, Zucchi et al. 1969 for a review). These bees are thought to have specific foraging routes known as "traplines" where they visit the same flowering individuals in particular sequence on a daily basis. Janzen (1971) noted that females often fly these circuits about the same time on consecutive days. The plants incorporated in traplines are "steady state" bloomers (terminology: Gentry 1974) which produce few flowers each day and flower over a long period (Janzen 1971). Although traplining behavior implies site fidelity, Janzen (1971) reports that females can fly considerable distances rapidly so that a given trapline may cover a large area. Male euglossine bees may visit the same nectar hosts as females (Zucchi et al. 1969 for a review). However, their foraging behavior may be very different (Kroodsma 1975) because males are thought to lead the nomadic, "vagabond" life (Dodson 1970, Dodson et al. 1969). Unlike females of some species, once males eclose they leave the nest never to return (Dodson 1966, Zucchi et al. 1969, Roberts and Dodson 1967). Individual males may spend each night at a different locality (Williams and Dodson 1972) although exceptions have been noted (Dodson 1966). Like female euglossine bees-, males are capable of rapid, long-distance flight and have been seen flying several kilometers over open water and across Andean mountain passes (Dodson in Dressler 1968; Dressler 1968; Janzen 1971; Ackerman pers. obs. 1979, 1980). However, since males are not tied to a nesting site, Williams and Dodson (1972) suggest that they have a wider foraging range than females, and Janzen (1981) suggests that they may occupy in great part different habitats from females. During August and September 1979, we studied the nectar-foraging behavior of two euglossine species, Euglossa imperialis (Cockerell) and Exaerete smaragdina (Guerin-Meneville), on Ca/athea latifolia (Willd. ex Link) Klotzsch (Marantaceae) at the Laboratory Clearing of Barro Colorado Island (BCI), Lake Gatun, Panama. We present evidence that male euglossines are not necessarily as transient and vagabond as portrayed and that their food-foraging behavior resembles that described for females. THE PLANT AND FLOWER VISITORS Calathea latifolia is common in central Panama where it grows at the forest edge and in adjacent, very often disturbed areas (Kennedy 1978). It is common in the Laboratory Clearing and sparse in the surrounding secondary and primary tropical moist forest. It is an herbaceous, rhizomatous perennial, up to 2.5 m tall (mostly 1-1.5 m at our site), and produces a single, cone-like, terminal inflorescence per aerial shoot. Flowers are produced continuously for several months BIOTROPICA 14(4): 241-248 1982 241 lPresent address: Department of Biology, University of Puerto Rico, Rio Piedras, Puerto Rico 00931, U.S.A. This content downloaded from 207.46.13.111 on Tue, 09 Aug 2016 04:40:13 UTC All use subject to http://about.jstor.org/terms duri.ng the rainy season. We found an average of 7.4 flowers per inflorescence (n 102, s.d. 3.6) along Pipeline Road (north of Gamboa, Panama). Kennedy (1978) reported a slightly smaller average (5.1, n=45). Each flower lasts one day. Flowers of C. latifolia do not open spontaneously so the first forager must force open the bud to feed on the nectar. An unopened, unvisited flower contains an average of 14 pul of nectar (n= 52, s.d.= 4.9) composed of 38.5 percent sugar (weight by total weight, n _ 24, s.d. 3.9). Nectar samples were drawn from flowers collected between 0800 and 0830. Sugar content from these was determined by pooling contents of two flowers per sample in order to obtain a pocket-refractometer reading. The nectar reward is comparable to other bee-pollinated neotropical plants (Baker 1978). Calathea latifolia is visited by a variety of euglossine bees across its range (Kennedy 1978), and is successfully pollinated by many. The most important pollinators on BCI were Eg. imperialis and Ex. smaragdina. Euglossa imperialis is medium-sized, 13-16 mm long, and is common in lowland forests of central Panama (Ackerman 1981). Exaerete smaragdina is a larger bee, relatively uncommon, 18-20 mm long, and a nest parasite of other large euglossines, e.g., Eulaemra nigrita Lepeliter (Kimsey 1979). It is never as abundant as Eg. imperialis in central Panama. Less commonly observed visitors were Eulaema meriana (Oliver), Eulaemat leucopyga (Friese), El. nigrita, and Exaerete frontalis (GuerinMeneville).

Male Euglossa imperiialis (Apidae, Euglossini) were marked after capture at cineole, a compound in orchid floral fragrances. Recaptures revealed that a large number of males may be available for pollination of a given orchid and that individual bees may remain at one locality throughout a morning and may be recapturable at that site over a period of several days. THE POPULATION BIOLOGY of many tropical plant species is influenced by insect pollinator species. This situation is especially true of many neotropical orchids, where floral fragrances of a given species attract male bees of only one or a few species in the tribe Euglossini. The effective orchid population size is therefore related to (1) distances between orchids and (2) distances flown by the pollinating male euglossine bees. The spectacular pollination of orchid flowers by the male bees has been described in some detail (see Williams and Dodson 1972, for review), but little else is known about the males' life habits. They leave the nests after hatching and do not return (Dodson 1966, Roberts and Dodson 1967). At least some males spend the night sleeping in flowers (Dodson 1966), suggesting that foraging could begin from a different locality each day (Williams and Dodson 1972). Females of some species are communal in their nesting habits, but no worker and reproductive castes occur as are found in the Bombini, Meliponini, and Apini. Each female builds and provisions her own nest cells and lays her own egg therein. Such is the case for Euglossa imperialis and probably E. ignita; females of other species (e.g., Euglossa dodsoni) are solitary, with each female building her own nest (Roberts and Dodson 1967). The foraging behaviors of the sexes are possibly very different. Females have a definite "home," make regular flights to and from the nest (Janzen 1971), and do not visit orchid flowers, while males visit orchids as well as nectar hosts. The hypothesis that male euglossines may fly long distances between orchids (see Dressler 1968, Williams and Dodson 1972) is founded on several observations: (1) Janzen (1971) found that female Euplusi,a surinamensis may return to the nest when displaced as much as 23 km; the speedy return suggests that "bees were released in an area known to them and therefore probably within their foraging range." (2) The bees are very strong fliers, indicated by flights across 1-5 km of water (female Euplusia and Eulaema observed by Janzen 1971, sex not mentioned Dressler 1968) or 1000 m above normal foraging locations in the Andes (sex not mentioned, Dodson, in Dressler 1968). (3) Widely dispersed orchid individuals are presumably maintained by pollinators traversing considerable distances (Williams and Dodson 1972). Failure to recapture more than one or two marked male bees at a given point indicates (a) that bees are present in extraordinarily large numbers and recapture of a marked bee is an improbable event, (b) that bees range great distances and might therefore rarely return to a given location (Williams and Dodson 1972), or, less likely, (c) that marking is so traumatic that the bee dies or flees. Williams and Dodson (1972) further speculate that a large male euglossine bee should be capable of flying 24 km within a day, 40 km in a few days, and 80-90 km in a few days or a week. Such flight distances are certainly possible, for a honeybee (Apis mellif era ) has been shown to fly over 100 km/day in her many flights to and from the hive (von Frisch 1967). However, the actual distances flown by male euglossines are unknown, and preliminary mark-and-recapture experiments which I conducted during March 1972 at the Tropical Science Center building, Rincon de Osa, Costa Rica, suggest that the activity of some bees may in some instances be quite local. Between 0700 and 1130 on 4 March at a location on the Holdridge Trail, I captured 601 Euglossa males of approximately 15 species which were attracted to 4 cm2 blotters placed on the ground and sprinkled with cineole, one of several compounds which has been identified in orchid floral fragrances (Hills, Williams, and Dodson 1968). BIOTROPICA 7(1): 71-72 1975 71 This content downloaded from 207.46.13.57 on Fri, 09 Sep 2016 04:22:31 UTC All use subject to http://about.jstor.org/terms Seventy-five bees were marked with unique color combinations, and the remainder were simply marked with a spot of silver paint on the thorax. During the morning of 5 March I returned to the same location, again put out the blotters with cineole attractant, and captured 191 bees. On this day, detailed observations were made of the species E. imperialis Cockerell. I captured 126 individuals of this species; 22 had been marked the day before. Assuming the same proportion (126/191 0.66) of E. imperialis present in the 4 March sample where records for each species were not kept, and making all the assumptions of mark-recapture population estimates (including no immigration or emigration), the approximate number of imperialis males foraging at this locality was 2270. On 6 March I placed blotters with the cineole attractant at locations 5, 10, 15, and 20 minutes walking distance from the marking location (20 minutes was approximately 1.5 km), and sampled each location every 30-45 minutes between 0730 and 1100 for E. imperialis. Marked bees were still present in considerable numbers (see table 1). (The TABLE 1. Data on bee marking. 6 March distance from marking location 5 March E marking location ? No. marked bees 22 7 3 0 0 Total no. bees 126 54 60 10 16 Proportion marked 0.175 0.130 0.050 0.000 0.000 decreasing proportion of marked bees at increasing distances from the marking location probably reflects the increasing area over which marked bees could forage.) Observations of the individually marked bees indicated that the same bee might return to the cineole bait several times in the same morning. For example, a bee marked at 0750 was observed at the bait again at 0955 and 1032. Orchid flowers are undoubtedly less attractive than the bait, for one never sees 50 bees at the same flower. In addition, the data presented here are subject to the biases of small sample sizes, but especially to the biases introduced by the use of supernormal concentrations of attractants which could conceivably alter normal foraging habits. Under the experimental conditions used, the data reveal that a large number of male bees (E. imperialis were especially abundant) may forage at one site and that individual bees may remain in one locality throughout a morning and may be recapturable over a period of several days. This finding is in contrast with the extremely low recapture rates published by others (Williams and Dodson 1972), and should encourage further study of the distances flown by male euglossines and of the role which the bees play in the population biology of orchids.