Fields of flowers with few strikes: how oligolectic bees manage their foraging behavior on Calibrachoa elegans (Solanaceae).

In specialized plant-pollinator associations, partners may exhibit adaptive traits, which favor the maintenance of the interaction. The association between Calibrachoa elegans (Solanaceae) and its oligolectic bee pollinator, Hexantheda missionica (Colletidae), is mutualistic and forms a narrowly specialized pollination system. Flowers of C. elegans are pollinated exclusively by this bee species, and the bees restrict their pollen resources to this plant species. The pollen presentation schedules of C. elegans were evaluated at the population level to test the hypothesis that H. missionica females adjust their foraging behavior to the resource offering regime of C. elegans plants. For this, the number of new flowers and anthers opened per hour (as a proxy for pollen offering) was determined, and pollen advertisement was correlated with the frequency of flower visits during the day. Preferences of female bees for flowers of different stages were also investigated, and their efficiency as pollinators was evaluated. Pollen offering by C. elegans was found to be partitioned throughout the day through scattered flower openings. Females of H. missionica indeed adjusted their foraging activity to the most profitable periods of pollen availability. The females preferred new, pollen-rich flowers over old ones and gathered pollen and nectar selectively according to flower age. Such behaviors must optimize female bee foraging efficiency on flowers. Female bees set 93% of fruit after a single visit. These findings guarantee their importance as pollinators and the persistence of the specialized plant-pollinator association.

A new neopasiphaeine bee associated with flowers of Loasaceae (Hymenoptera: Colletidae: Actenosigynes).

The genus Actenosigynes includes two species, A. fulvoniger (Michener, 1989) and A. mantiqueirensis Silveira, 2009, both oligolectic on flowers of Blumenbachia (Loasaceae) in southern Brazil. We describe a third species, Actenosigynes silveirai Siriani-Oliveira, sp. n., and provide additional evidence to the suspected narrow host-plant specificity between bees of this genus and Loasaceae. This new species was only recorded to collect resources on flowers of Aosa, a genus closely related to Blumenbachia in the subfamily Loasoideae. We illustrate female and male specimens of the three species to offer a complete summary of the morphological variation within this modestly sized genus of Neopasiphaeinae, including photographs of male genitalia and associated metasomal sterna. Moreover, we provide an identification key for the three species of Actenosigynes and the first phylogenetic and dating estimate for these taxa. The genus diversified in southern South America during the Miocene-Pliocene, following a more ancient divergence associated with the orogenic events that separated its sister-genus, Torocolletes, west of the Andes. We dedicate this newly described species to Fernando A. Silveira for his contributions to research on Brazilian bee taxonomy and biology.

Minimum size threshold of visiting bees of a buzz-pollinated plant species: consequences for pollination efficiency.

PREMISE: Flowering plants with poricidal anthers are commonly visited by buzzing bees, which vibrate flowers to extract pollen. However, not all flower visitors are in fact pollinators, and features such as body size and duration of flower visits are important factors in determining pollination effectiveness. We tested whether bee-to-flower size relationships predict the pollination effectiveness of flower visitors of a buzz-pollinated species (Chamaecrista ramosa, Fabaceae). METHODS: We sorted 13 bee taxa into three groups: smaller than, equivalent to ("fit-size"), and larger than flower herkogamy (spatial separation between anthers and stigma). We expected the latter two groups to touch the stigmas, which would be an indicator of pollination effectiveness, more frequently than the first group. To test this hypothesis, we assessed contact with stigmas, foraging behavior, and duration of visits for the three size groups of bees. RESULTS: Our data reveal that small bees scarcely touched the stigmas, while large and fit-size bees were the most efficient pollinators, achieving high stigma-touching rates, conducting much shorter flower visits, and visiting flowers and conspecific plants at high rates during foraging bouts. CONCLUSIONS: The results did not show size-matching among bees and flowers, as expected, but rather a minimum size threshold of efficient pollinators. The finding of such a threshold is a nonarbitrary approach to predicting pollination effectiveness of visitors to herkogamous flowers with poricidal anthers.

Light intensity regulates flower visitation in Neotropical nocturnal bees.

The foraging activity of diurnal bees often relies on flower availability, light intensity and temperature. We do not know how nocturnal bees, which fly at night and twilight, cope with these factors, especially as light levels vary considerably from night to day and from night to night due to moon phase and cloud cover. Given that bee apposition compound eyes function at their limits in dim light, we expect a strong dependence of foraging activity on light intensity in nocturnal bees. Besides being limited by minimum light levels to forage, nocturnal bees should also avoid foraging at brighter intensities, which bring increased competition with other bees. We investigated how five factors (light intensity, flower availability, temperature, humidity, and wind) affect flower visitation by Neotropical nocturnal bees in cambuci (Campomanesia phaea, Myrtaceae). We counted visits per minute over 30 nights in 33 cambuci trees. Light intensity was the main variable explaining flower visitation of nocturnal bees, which peaked at intermediate light levels occurring 25 min before sunrise. The minimum light intensity threshold to visit flowers was 0.00024 cd/m2. Our results highlight the dependence of these nocturnal insects on adequate light levels to explore resources.

Starmera foglemanii sp. nov. and Starmera ilhagrandensis sp. nov., two novel yeast species isolated from ephemeral plant substrates.

Four isolates of two novel ascosporogenous species belonging to the clade Starmera were obtained from cactus tissues and rotting wood in Brazil. Results of analyses of the sequences of the ITS and D1/D2 domains of the large subunit rRNA gene indicated that the two isolates of the cactophilic species are related to Starmera caribaea and Starmera pilosocereana, yeasts that are associated with cacti and require an organic source of sulfur for growth. We propose the novel species Starmera foglemanii sp. nov. (CBS 16113T; MycoBank number: MB 834400) to accommodate these isolates. The other two isolates are phylogenetically related to Candida dendrica, Candida laemsonensis and Candida berthetii, also in the Starmera clade. The novel species name Starmera ilhagrandensis sp. nov. (CBS 16316T; MycoBank number: MB 834402) is proposed for this species.

Nectar Secretion of Floral Buds of Tococa guianensis Mediates Interactions With Generalist Ants That Reduce Florivory.

The specialised mutualism between Tococa guianensis and ants housed in its leaf domatia is a well-known example of myrmecophily. A pollination study on this species revealed that flowers in the bud stage exude a sugary solution that is collected by ants. Given the presence of this unexpected nectar secretion, we investigated how, where, and when floral buds of T. guianensis secret nectar and what function it serves. We studied a population of T. guianensis occurring in a swampy area in the Cerrado of Brazil by analyzing the chemical composition and secretion dynamics of the floral-bud nectar and the distribution and ultrastructure of secretory tissues. We also measured flower damage using ant-exclusion experiments. Floral bud nectar was secreted at the tip of the petals, which lack a typical glandular structure but possess distinctive mesophyll due to the presence of numerous calcium oxalate crystals. The nectar, the production of which ceased after flower opening, was composed mainly of sucrose and low amounts of glucose and fructose. Nectar was consumed by generalist ants and sporadically by stingless bees. Ant exclusion experiments resulted in significantly increased flower damage. The floral nectar of T. guianensis is produced during the bud stage. This bud-nectar has the extranuptial function of attracting generalist ants that reduce florivory. Pollen is the unique floral resource attracting pollinators during anthesis. Tococa guianensis, thus, establishes relationships with two functional groups of ant species: specialist ants acting against herbivory and generalist ants acting against florivory.

Nocturnal floral scent profiles of Myrtaceae fruit crops.

Communication between plants and nocturnal pollinators in low light conditions is mainly guided by floral scents, which is well documented for plants pollinated by bats, moths, and beetles. Just recently, nocturnal bees have been added to the list of pollinators known to respond to floral scents of their host plants. Little is known about the floral scent chemistry of plants visited and pollinated by nocturnal bees. Among these plants are economically important fruit crops of the family Myrtaceae. We aimed to analyze the nocturnal floral scent profiles of 10 species of Myrtaceae (only diurnal P. cattleianum was sampled after sunrise) and address the following questions: i) What are the main floral scent compounds emitted by the species? ii) Are the floral scent profiles similar to those described for other species pollinated by nocturnal bees? Floral scents were collected by dynamic headspace and analyzed by GC-MS (gas chromatography - mass spectrometry). The total amount of scent trapped ranged from 74 ng/flower/hour for Syzygium malaccense to 7556 ng/flower/hour for Eugenia dysenterica. A total of 46 floral scent compounds were detected in the samples with the most abundant compounds being the aromatics benzaldehyde, benzyl alcohol, 2-phenylethanol, methyl salicylate, 2-phenylethyl acetate, and benzyl acetate; the aliphatic compound 1-octanol; and the monoterpene linalool. The different species exhibited different relative scent patterns. Overall, the nocturnal scents of the studied species of Myrtaceae are dominated by aromatic compounds, which is in contrast to the scent profiles described for other plants pollinated by nocturnal bees.

Osmophores of Caryocar brasiliense (Caryocaraceae): a particular structure of the androecium that releases an unusual scent.

Caryocar brasiliense is a flagship species of the Brazilian Cerrado. It produces flowers with a strong peculiar scent, which are pollinated by bats and occasionally moths with short mouthparts. However, the cues responsible for attracting these nocturnal pollinators remain unknown. We aimed to identify osmophores of C. brasiliense, describe the ultrastructure of the cells involved in the synthesis and release of floral odour, and identify the constituents of the floral bouquet. We performed field observations and histochemical and ultrastructural analyses of flowers focusing on the androecium. Gas chromatography-mass spectrometry was used to analyse the scents emitted. Filament epidermal cells were found to possess an unusual shape and be responsible for the main production and release of odour. These cells, called foraminous cells, are elongate and possess pores where their cell walls are abruptly thin. The cuticle is practically absent over the pores, which facilitates odour emission. The foraminous cells have conspicuous nuclei and organelle-rich cytoplasm where oil droplets can be seen prior to anthesis. The features of these cells remain similar during anthesis, but many vesicles fuse with the plasma membrane and the number of oil droplets in the cytosol decreases. Twenty-nine components were found in the scent, especially fatty acid derivatives and N- and S-bearing compounds. Our analyses revealed that the androecium of C. brasiliense has a particular structure that acts as an osmophore. The scent from the androecium resembles that of the entire flower, which is an unprecedented finding for a plant with single flowers as the pollination unit.

Nocturnal Bee Pollinators Are Attracted to Guarana Flowers by Their Scents.

Floral scent is an important component of the trait repertoire of flowering plants, which is used to attract and manipulate pollinators. Despite advances during the last decades about the chemicals released by flowers, there is still a large gap in our understanding of chemical communication between flowering plants and their pollinators. We analyzed floral scents of guarana (Paullinia cupana, Sapindaceae), an economically important plant of the Amazon, using chemical analytical approaches, and determined the attractiveness of the scent to its nocturnal bee pollinators using behavioral assays in the field. Pollen loads of attracted bees were also analyzed. Inflorescences of guarana emit strong scents, both during day and at night, with some semi-quantitative differences between day- and night-time scents. Synthetic scent mixtures containing some of the identified floral scent components, including the most abundant ones, i.e., linalool and (E)-ß-ocimene, successfully attracted the nocturnal Megalopta bee pollinators. Pollen analyses revealed that many of the attracted bees had pollen grains from previous visits to guarana flowers on their bodies. Overall, our data show that guarana flowers attract nocturnal bee visitors by their strong scents and suggest that the chemical communication between this plant and its pollinators is a key component in crop production of this economically important plant species.

Floral colour change in Byrsonima variabilis (Malpighiaceae) as a visual cue for pollen but not oil foraging by oil-collecting bees.

Pollinators search for multiple flora resources throughout their life cycle. Most studies, however, only assess how bees discriminate floral cues in the context of nectar foraging. In the present study, we sought to elucidate whether oil-collecting bees discriminate flowers of Byrsonima variabilis (Malpighiaceae) with petals of different colours when foraging for pollen or oil. As the colour of the standard petal changes during anthesis, we characterised the spectral reflectance patterns of flowers throughout anthesis and modelled chromatic perceptual space to determine how these colour patterns are perceived by bees. Through the quantification of flower pollen in the different phases, we found that the colour of the standard petal is an honest cue of the presence of pollen. Centridine bees preferentially visited flowers with a yellow (bee's green) colour when searching for pollen, but indiscriminately visited flowers with different petal colours when searching for floral oil. We suggest that standard petals, in the species studied and others of the genus, like nectar guides, act as pollen guides, which oil-collecting females use to detect pollen-rich flowers. Moreover, they use different floral clues during foraging for different resources in the same host plant.

Unveiling the osmophores of Philodendron adamantinum (Araceae) as a means to understanding interactions with pollinators.

Background and Aims: Araceae species pollinated by nocturnal Cyclocephalini beetles attract their pollinators by inflorescence scents. In Philodendron , despite the intense odour, the osmophores exhibit no definite morphological identity, making them difficult to locate. This may explain why structural studies of the scent-releasing tissue are not available so far. Methods: Several approaches were employed for locating and understanding the osmophores of Philodendron adamantinum . A sensory test allowed other analyses to be restricted to fertile and sterile stamens as odour production sites. Stamens were studied under light and electron microscopy. Dynamic headspace and gas chromatography-mass spectrometry were used to collect and analyse scents from different zones of the inflorescence. Key Results: The epidermal cells of the distal portion of fertile stamens and staminodes are papillose and, similar to the parenchyma cells of this region, have dense cytoplasm and large nuclei. In these cells, the composition of organelles is compatible with secretory activity, especially the great number of mitochondria and plastids. In this portion, lipid droplets that are consumed concomitantly with the release of odour were observed. Quantitative scent analyses revealed that the scent, with a predominance of dihydro-ß-ionone, is mainly emitted by the fertile and sterile staminate zones of the spadix. An amorphous substance in the stomata pores indicates that the components are secreted and volatilized outside of the osmophore under thermogenic heat. Conclusions: Despite the difficulty in locating osmophores in the absence of morphological identity and inefficiency of neutral red staining, the osmophores of P. adamantinum have some features expected for these structures. The results indicate a functional link between thermogenesis and volatilization of osmophore secretions to produce olfactory signals for attracting specialized beetle pollinators. These first experimental data about the precise location of osmophores in Philodendron will stimulate studies in related species that will allow future comparison and the establishment of patterns of functional morphology.

Pollination biology in the dioecious orchid Catasetum uncatum: How does floral scent influence the behaviour of pollinators?

Catasetum is a neotropical orchid genus that comprises about 160 dioecious species with a remarkable sexual dimorphism in floral morphology. Flowers of Catasetum produce perfumes as rewards, which are collected only by male euglossine bees. Currently, floral scents are known to be involved in the selective attraction of specific euglossine species. However, sexual dimorphism in floral scent and its eventual role in the pollination of Catasetum species have never been investigated. Here, we have investigated the pollination of Catasetum uncatum and asked: (1) Is floral scent a sexual dimorphic trait? (2) Does pollinarium removal/deposition affect scent emission? (3) Does sexual dimorphism in floral scent and changed scent emission have implications with regard to the behaviour of the pollinators? The frequency and behaviour of floral visitors were observed in non-manipulated flowers (both flower sexes) and in manipulated flowers (pistillate only) in which pollinaria were deposited. Scents of staminate and pistillate flowers (both manipulated and non-manipulated) were collected by using dynamic headspace methods and analysed chemically. Electrophysiological analyses were performed to detect compounds triggering antennal depolarisation in the euglossine species. C. uncatum is pollinated mainly by males of Euglossa nanomelanotricha. Pollinators were more frequent in pistillate than in staminate inflorescences. Bees approaching staminate flowers frequently flew away without visiting them, a behavioural pattern not observed in pistillate flowers. In the chemical analyses, we recorded 99 compounds, 31 of which triggered antennal depolarisation in pollinators. Multivariate analyses with the electrophysiological-active compounds did not detect differences between the scent composition of staminate and pistillate flowers. Pollinarium removal or deposition resulted in diminished scent emission within 24h in staminate and pistillate flowers, respectively. Surprisingly, bees discriminated pollinated from non-pollinated pistillate flowers as early as 2h after pollination. The rapid loss in the attractiveness of flowers following pollinarium removal/deposition can be interpreted as a strategy to direct pollinators to non-pollinated flowers. We have found no evidence that euglossine males discriminate staminate from pistillate flowers by means of floral scent. Instead, we speculate that bees use visual cues, such as sex dimorphic traits, to discriminate flowers of different sexes. Together, our results provide interesting insights into the evolution of floral signals in gender-dimorphic species and into its significance in plant reproductive biology.

An aromatic volatile attracts oligolectic bee pollinators in an interdependent bee-plant relationship.

Chemical signals emitted by the plant frequently mediate host-plant localization in specialized animal - plant associations. Studying the interdependent highly specialized association of the narrowly oligolectic bee pollinator Protodiscelis palpalis (Colletidae, Neopasiphaeinae) with Hydrocleys martii (Alismataceae) in ephemeral aquatic water bodies in semi-arid Caatinga of Brazil, we asked if specific volatile compounds produced by the flowers mediate pollinator attraction. The yellow Hydrocleys flowers are the sole pollen and nectar resources, and mating sites for the bees. We analyzed the floral scents of this species and of the closely related H. nymphoides, which is not visited by P. palpalis, and tested the main volatile compounds of both species under field conditions to evaluate their attractiveness to bees of P. palpalis. Methoxylated aromatics were the dominant floral scent components in both species, but each species exhibited a characteristic scent profile. Dual choice bioassays using artificial flowers made of yellow and blue adhesive paper clearly revealed that ρ-methylanisole alone, the dominant volatile of H. martii, attracted significantly more bees than unbaited flowers. This compound represents an olfactory communication channel used by the plant that lures its effective oligolectic pollinators to its flowers. Yellow artificial flowers baited significantly more bees than blue ones. Our study reinforces the recent findings that specific compounds in complex floral scent bouquets are crucial for host-plant location in oligolectic bees.

The chemical basis of host-plant recognition in a specialized bee pollinator.

Many pollinators specialize on a few plants as food sources and rely on flower scents to recognize their hosts. However, the specific compounds mediating this recognition are mostly unknown. We investigated the chemical basis of host location/recognition in the Campanula-specialist bee Chelostoma rapunculi using chemical, electrophysiological, and behavioral approaches. Our findings show that Ca. trachelium flowers emit a weak scent consisting of both widespread and rare (i.e., spiroacetals) volatiles. In electroantennographic analyses, the antennae of bees responded to aliphatics, terpenes, aromatics, and spiroacetals; however, the bioassays revealed a more complex response picture. Spiroacetals attracted host-naive bees, whereas spiroacetals together with aliphatics and terpenes were used for host finding by host-experienced bees. On the intrafloral level, different flower parts of Ca. trachelium showed differences in the absolute and relative amounts of scent, including spiroacetals. Scent from pollen-presenting flower parts elicited more feeding responses in host-naive bees as compared to a scentless control, whereas host-experienced bees responded more to the nectar-presenting parts. Our study demonstrates the occurrence of learning (i.e., change in the bee's innate chemical search-image) after bees gain foraging experience on host flowers. We conclude that highly specific floral volatiles play a key role in host-flower recognition by this pollen-specialist bee, and discuss our findings into the broader context of host-recognition in oligolectic bees.

The floral scent of Taccarum ulei (Araceae): attraction of scarab beetle pollinators to an unusual aliphatic acyloin.

The strongly fragrant thermogenic inflorescences of Taccarum ulei (Araceae) are highly attractive to night-active scarab beetles of Cyclocephala celata and C. cearae (Scarabaeidae, Cyclocephalini), which are effective pollinators of plants in the wild in northeastern Brazil. GC-MS analysis of headspace floral scent samples of T. ulei established that two constituents, (S)-2-hydroxy-5-methyl-3-hexanone (an aliphatic acyloin rarely detected in flowers) and dihydro-ß-ionone (an irregular terpene) accounted for over 96% of the total scent discharge. Behavioral tests (in both field and cages) showed that male and female C. celata and C. cearae were attracted to traps baited with a synthetic mixture of both compounds; however, they were also responsive to (S)-2-hydroxy-5-methyl-3-hexanone alone, which thus functions as a specific attractive cue. These findings support other recent research in suggesting that angiosperms pollinated by cyclocephaline scarab beetles release floral odors of limited complexity in terms of numbers of compounds, but often dominated by unusual compounds that may ensure attraction of specific pollinator species.

The key role of 4-methyl-5-vinylthiazole in the attraction of scarab beetle pollinators: a unique olfactory floral signal shared by Annonaceae and Araceae.

Cyclocephaline scarabs are specialised scent-driven pollinators, implicated with the reproductive success of several Neotropical plant taxa. Night-blooming flowers pollinated by these beetles are thermogenic and release intense fragrances synchronized to pollinator activity. However, data on floral scent composition within such mutualistic interactions are scarce, and the identity of behaviorally active compounds involved is largely unknown. We performed GC-MS analyses of floral scents of four species of Annona (magnoliids, Annonaceae) and Caladium bicolor (monocots, Araceae), and demonstrated the chemical basis for the attraction of their effective pollinators. 4-Methyl-5-vinylthiazole, a nitrogen and sulphur-containing heterocyclic compound previously unreported in flowers, was found as a prominent constituent in all studied species. Field biotests confirmed that it is highly attractive to both male and female beetles of three species of the genus Cyclocephala, pollinators of the studied plant taxa. The origin of 4-methyl-5-vinylthiazole in plants might be associated with the metabolism of thiamine (vitamin B1), and we hypothesize that the presence of this compound in unrelated lineages of angiosperms is either linked to selective expression of a plesiomorphic biosynthetic pathway or to parallel evolution.

Nocturnal bees are attracted by widespread floral scents.

Flower localization in darkness is a challenging task for nocturnal pollinators. Floral scents often play a crucial role in guiding them towards their hosts. Using common volatile compounds of floral scents, we trapped female nocturnal Megalopta-bees (Halictidae), thus uncovering olfactory cues involved in their search for floral resources. Applying a new sampling method hereby described, we offer novel perspectives on the investigation of nocturnal bees.

New records for species of Theope (Lepidoptera, Riodinidae) for the state of Pernambuco and northeastern Brazil, with notes on their natural history

New records for species of Theope (Lepidoptera, Riodinidae) for the state of Pernambuco and northeastern Brazil, with notes on their natural history. Five new records for the state of Pernambuco and one new record for NE-Brazil are reported in this paper for the genus Theope. Relationship between ants and T. terambus was observed for the first time which also consists on the first ever recorded myrmecophilous interaction between Pheidole ants and a Theope immature. Schoepfia guianensis is reported as a probable hostplant for T. terambus. Illustrations of seven species of Theope which occur in the northeastern Atlantic Rainforest are provided.

Novas ocorrências do gênero Theope (Lepidoptera, Riodinidae) para Pernambuco e Nordeste brasileiro e comentários de sua história natural. São registradas cinco novas ocorrências do gênero Theope para Pernambuco e uma nova ocorrência para o Nordeste do Brasil. É relatada pela primeira vez relação mirmecófila para T. terambus, assim como uma relação entre um imaturo de Theope e formigas do gênero Pheidole. Schoepfia guianensis é relatada como provável planta hospedeira de T. terambus. São fornecidas ilustrações para as sete espécies de Theope registradas nesse estudo.

Mutual reproductive dependence of distylic Cordia leucocephala (Cordiaceae) and oligolectic Ceblurgus longipalpis (Halictidae, Rophitinae) in the Caatinga.

BACKGROUND AND AIMS: The close relationship between distylic Cordia leucocephala and the bee Ceblurgus longipalpis, both endemic to the Caatinga, north-east Brazil, was investigated, emphasizing reproductive dependence, morphological adaptations of the partners, and pollen flow. METHODS: In the municipality of Pedra, in the Caatinga of Pernambuco, the breeding system and reproductive success of C. leucocephala, its interaction with flower visitors and inter- and intramorph pollen flow were determined. KEY RESULTS: The bee Ceblurgus longipalpis, the unique flower visitor and effective pollinator of self-incompatible Cordia leucocephala, presents morphological features adapted to exploit hidden pollen and nectar in the long and narrow corolla tubes. Pollen of low-level anthers is collected with hairs on prolonged mouthparts and pollen of high-level anthers with clypeus, mandibles, and labrum, showing pollen removal from both levels with the same effectiveness. In both morphs, this results in similar legitimate, i.e. intermorph cross-pollen flow. Illegitimate pollen flow to stigmas of pin flowers, however, was much higher than to stigmas of thrum flowers. Moreover, more illegitimate pollen was transported to stigmas of pin and less to those of thrum flowers when compared with legitimate pollen flow. CONCLUSIONS: The study reveals a one-to-one reproductive inter-dependence between both partners. Data indicate that this relationship between bee species and plant species is one of the rare cases of monolecty among bees. Monotypic Ceblurgus longipalpis, the only rophitine species of Brazil, evolved prolonged mouthparts rare among short-tongued bees that enable them to access pollen from flowers with short-level anthers hidden for bees of other species, and nectar at the base of the flower tube.

[The gallery forests of the São Francisco river as corridors for Euglossine bees (Hymenoptera: Apidae) from tropical rainforests]. / Mata ciliar do Rio São Francisco como biocorredor para Euglossini(Hymenoptera: Apidae) de florestas tropicais úmidas.

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.