Nectar Robbers Research Articles

Multiscale spatial analysis of two plant–insect interactions: effects of landscape, resource distribution, and other insects

ContextBiotic resource exploitation is a critical determinant of species’ distributions. However, quantifying resource exploitation patterns through space and time can be difficult, complicating their incorporation in spatial ecology studies. Therefore, understanding the local drivers of spatial patterns of resource exploitation may contribute to better large-scale species distribution models.ObjectivesWe investigated (1) how the resource exploitation patterns of two trophic interactions (plant–insect) are explained by insect behaviour, resource aggregation, and potential insect-insect interactions. We also analyzed how (2) resource patch size and (3) resource accessibility in a heterogeneous landscape affected host exploitation patterns.MethodsWe quantified nectar robbing by insects in the genus Bombus (bumblebees) and seed predation by Brachypterolus vestitus larvae (Antirrhinum beetle) on Antirrhinum majus L. (wild snapdragons) in the Pyrenees Mountains, Catalonia, Spain. We tested hypotheses about resource exploitation by integrating spatial analyses at multiple scales.ResultsBoth trophic interactions were aggregated, explained by the aggregation of their resource. At some scales, nectar robbing is more aggregated than the resource. Trophic interaction abundance is proportional to resource patch size, following the ideal free distribution model. Landscape features do not explain the locations exploited. Nectar robbing and seed predation occur together more often than expected.ConclusionsOur findings suggest that multiple biotic and ecological spatial factors may simultaneously affect resource exploitation at a local scale. These findings should be considered when developing agricultural projects, management plans and conservation policies.

Long corolla flowers in Tropical Andes favour nectar robbing by the Black Metaltail hummingbird: A study using citizen science and field observations

AbstractUnderstanding what drives the evolution of nectar‐robbing strategies is key for gaining insight into the functioning of pollination networks. However, nectar robbing is often an anecdotal behaviour, difficult to quantify and record through field observations, especially in hummingbirds, limiting our understanding of how ecological networks change across communities. Here, we report new records of nectar robbing by Peru's endemic Black Metaltail (Metallura phoebe) in a high‐elevation forest at ca. 4000 m a.s.l. and how this species uses either legitimate pollination feeding or nectar robbing in relation to corolla lengths. Furthermore, by analysing 452 citizen science records of photographic observations, we found that 36% of the photographs depicting a foraging event in this species were actually nectar‐robbing events. After identifying the plant species in all photographs involving foraging events, we describe how nectar robbing conducted by this hummingbird species is strongly associated with flowers that have longer corollas. We propose that the hummingbird‐flower interactions in harsh high‐altitude environments, where resources and competition vary markedly across seasons, can offer insight into the ecological drivers of nectar‐robbing behaviour in hummingbirds.

Flower-visiting lizards as key ecological actors for an endemic and critically endangered plant in the Canary Islands

Oceanic islands are places where biological assemblages are relatively simple, as compared to the mainland. On islands, however, pollinator assemblages may to be composed of a taxonomically disparate group of organisms (e.g. insects, lizards, and birds), some of them with opportunistic nectar-feeding behaviour. Here we investigated some components of pollination effectiveness of Lotus maculatus (Fabaceae), an endangered Canary Islands endemic. In a flower exclusion experiment, we bagged flowers and compared their subsequent fruit and seed set to that of control flowers. Number of interactions with vertebrate and invertebrate flower visitors was counted and it was recorded whether interactions were legitimate (potentially pollinating) or non-legitimate (nectar robbing). Additionally, we estimated pollen loads on lizards and looked for any relationship between reproductive success of individual plants and number of visits made by the top three flower-visiting species (in terms of both frequency of occurrence at censuses and number of floral visits). Bagged flowers fruited less and with fewer seeds than control flowers. The only observed flower-visiting vertebrate was the Tenerife lizard Gallotia galloti, whose interactions were always legitimate and with around a half of captured individuals carrying pollen grains. The most frequent flower-visiting insect was the honeybee Apis mellifera followed by the solitary bee Lasioglossum arctifrons. The honeybee, however, was only a nectar robber, and the solitary bee was not an effective pollinator, but rather a pollen gatherer. Fruit set by individual plants was positively related only to frequency of visits by the lizard. Thus, the lizard seems to play a key role in the conservation management of L. maculatus.

Ultrastructure and development of the floral nectary from Borago officinalis L. and phytochemical changes in its secretion

Although Boraginaceae have been classified as good sources of nectar for many insects, little is still known about their nectar and nectaries. Thus, in the present contribution, we investigated the nectar production dynamics and chemistry in Borago officinalis L. (borage or starflower), together with its potential interaction capacity with pollinators. A peak of nectar secretion (∼5.1 µL per flower) was recorded at anthesis, to decrease linearly during the following 9 days. In addition, TEM and SEM analyses were performed to understand ultrastructure and morphological changes occurring in borage nectary before and after anthesis, but also after its secretory phase. Evidence suggested that nectar was transported by the apoplastic route (mainly from parenchyma to epidermis) and then released essentially by exocytotic processes, that is a granulocrine secretion. This theory was corroborated by monitoring the signal of complex polysaccharides and calcium, respectively, via Thiéry staining and ESI/EELS technique. After the secretory phase, nectary underwent degeneration, probably through autophagic events and/or senescence induction. Furthermore, nectar (Nec) and other flower structures (i.e., sepals, gynoecia with nectaries, and petals) from borage were characterized by spectrophotometry and HPLC-DAD, in terms of plant secondary metabolites, both at early (E-) and late (L-) phase from anthesis. The content of phytochemicals was quantified and discussed for all samples, highlighting potential biological roles of these compounds in the borage flower (e.g., antimicrobial, antioxidant, staining effects). Surprisingly, a high significant accumulation of flavonoids was registered in L-Nec, with respect to E-Nec, indicating that this phenomenon might be functional and able to hide molecular (e.g., defence against pathogens) and/or ecological (e.g., last call for pollinators) purposes. Indeed, it is known that these plant metabolites influence nectar palatability, encouraging the approach of specialist pollinators, deterring nectar robbers, and altering the behaviour of insects.

Nectar robbing effects on pollinators of a key nectar source plant (Tecoma fulva, Bignoniaceae) in a dry tropical Andean valley

AbstractZoophilous flowering plants have features to attract their pollinators, which may also be used by exploiters like nectar robbers. Nectar robbers access nectar by probing flower corollas (primary robbing) or use existing holes (secondary robbing). Nectar robbing can negatively impact a plant's fitness directly by damaging the reproductive structures of the flower or indirectly by modifying the visitation patterns of pollinators. We tested the hypothesis that the robbed flowers are less visited by legitimate pollinators by comparing floral visitors and visitation frequency in primary‐, secondary‐, and un‐robbed flowers of Tecoma fulva spp. Altoandina, a native shrub species that is an important nectar source for nectarivores in the dry valleys of the Bolivian Andes (Bignoniaceae). The Giant Hummingbird, Patagona gigas (Trochilidae), was the main visitor of T. fulva and visited more frequently un‐robbed flowers, followed by secondary robbed and primary robbed flowers. The variation in visitation frequency may result in less pollen transport to robbed flowers, which may have negative consequences for the biological fitness, probably manifested in decreased seed production.Abstract in Spanish is available with online material.

Effect of robbing intensity on reproductive success of Symphytum officinale (Boraginaceae).

The intervention of nectar robbers in plant pollination systems will cause some pollinators to modify their foraging behavior to act as secondary robbers, consequently adopting a mixed foraging strategy. The influence of nectar robbing on pollinator behavior may be affected by spatio-temporal difference of robbing intensity, and consequently, may have different effects on the pollination of host plants. However, whether and how the nectar robbing might influence pollinators under different robbing intensity still needs further investigation. In this study, Symphytum officinale was used to detect the effect of nectar robbers on pollinators under different robbing intensity as well as their effects on plant reproductive success. Six robbing levels and three bumblebees with mixed foraging behaviors were used to evaluate the effect of different robbing intensity on pollinator behavior, visitation rate, flower longevity and pollen deposition. Our results indicated that the robbing rate increased gradually with the proportion of robbed flowers, but which did not affect the frequency of legitimate visits. The increase of robbing rate promoted the corolla abscission, and then enhanced the self-pollen deposition, but which had no significant effect on cross-pollen deposition. These results indicate that the overall fitness of S. officinale was improved by combined self and cross-pollination modes when visited by both pollinators and nectar robbers simultaneously. Although nectar robbing is not uncommon, its consequences for pollination in the interaction web have not been well studied. Our results emphasize the significance of indirect impacts in mediating the adaptive outcomes of species interactions.

NECTAR ROBBING BY THE RED-TAILED COMET SAPPHO SPARGANURUS: THE VALUE OF CITIZEN SCIENCE TO DOCUMENT INFREQUENT BEHAVIOR IN BIRDS

Nectar robbing by hummingbirds, the extraction of nectar using perforations instead of the corolla, is seldom documented in the literature. Here, we present the first photographic record of nectar robbing by the Red-tailed Comet Sappho sparganurus in Bolivia and examine published and photographic evidence of this behavior. We found no published evidence of nectar robbing by Red-tailed Comets in peer-reviewed literature. However, we found that about 4% of the photographs of hummingbird-flower interactions involving this species on citizen science platforms showed clear nectar robbing behavior. Our results suggest that nectar robbing is not an uncommon behavior for the Red-tailed Comet and highlight the hidden, yet immense, value of citizen science photographic databases to document avian natural history and behavior.

Lack of pollinators selects for increased selfing, restricted gene flow and resource allocation in the rare Mediterranean sage Salvia brachyodon

Range contraction and habitat fragmentation can cause biodiversity loss by creating conditions that directly or indirectly affect the survival of plant populations. Fragmented habitats can alter pollinator guilds and impact their behavior, which may result in pollen/pollinator limitation and selection for increased selfing as a mechanism for reproductive assurance. We used Salvia brachyodon, a narrowly distributed and endangered sage from eastern Adriatic, to test the consequences of range contraction and habitat fragmentation. Molecular data indicate a severe and relatively recent species range reduction. While one population is reproductively almost completely isolated, moderate gene flow has been detected between the remaining two populations. The high pollen-to-ovule ratio and the results of controlled hand pollination indicate that S. brachyodon has a mixed mating system. Quantitative and qualitative differences in the community and behaviour of flower visitors resulted in limited pollination services in one population where no effective pollinator other than pollen and nectar robbers were observed. In this population, self-pollination predominated over cross-pollination. Various environmental factors, in which plant-pollinator interactions play a pivotal role, have likely created selection pressures that have led to genetic and phenotypic differentiation and different resource allocation strategies among populations.

Nectar robbers and simulated robbing differ in their effects on nectar microbial communities

AbstractFloral nectar contains microbes that can influence nectar chemistry and pollinator visitation, and these microbial communities can be affected by pollinators in turn. Some flowers are also visited by nectar robbers, which feed on nectar through holes cut in floral tissue. If nectar robbers alter nectar microbial communities, they might have unexpected impacts on pollinator visitation. We investigated whether robbing could affect nectar microbial communities directly, by introducing microbes, or indirectly, by triggering a plant response to floral damage. We applied four treatments to flowers of Tecoma × “Orange Jubilee” (Bignoniaceae) in an arboretum setting: flowers were (1) covered to exclude all visitors; (2) available to both pollinators and nectar robbers and robbed naturally by carpenter bees; (3) available to pollinators only but cut at the base to simulate nectar robbing damage; or (4) available to pollinators only. We found that nectar in flowers accessible to any visitors was more likely to contain culturable microbes than flowers from which visitors were excluded. Microbial community composition and beta diversity were similar across treatments. Among flowers containing culturable microbes, flowers available to pollinators and nectar robbers had higher microbial abundance than flowers with simulated robbing, but there were no differences between flowers available to pollinators and robbers and unwounded flowers from which robbers were excluded. Overall, our results suggest that floral damage can affect some features of nectar microbial communities, but specific effects of nectar robbing are limited compared with the influence of visitation in general.

Floral visitors of sesame (Sesamum indicum L.): Elucidating their nectar-robbing behaviour and impacts on the plant reproduction.

Nectar robbing is common in angiosperms, especially in long tubular flowers or flowers with spurs that keep nectar out of reach of visitors. However, the robbing behaviour of bees is less understood. Here, we studied the sesame visitors, their robbing behaviour, and the impacts of robbing on plant reproductive fitness. Diverse insect species (primarily members of Hymenoptera) visited sesame flowers. The most effective pollinators were Amegilla zonata, Apis cerana, Apis dorsata, Apis florea, Ceratina binghami, Halictus acrocephalus and Xylocopa amethystina. Almost all visitors with variable percentages revealed the nectar-robbing phenomenon. Robbing activity depended on a complex of multiple attributes, including the visitor's body size, the corolla tube length, the availability and accessibility of nectar, and the resource-collecting task allocation of bees. Robbing activity varied according to flower-visiting species, flowering period and daytime. Robbing was comparatively higher in the late flowering period at 10.00-14.00 h. In the case of robbing visits, flower handling time was lower, and the visitation rate remained higher than non-robbing visits. Robbing visits did not significantly affect fruit and seed sets of sesame. Therefore, we can interpret the nectar-robbing interactions on sesame as commensal, with pollinators benefitting without altering the plant's reproductive fitness.

Pollination biology of Impatiens capensis Meerb. in non-native range.

Pollination biology in the widespread species Impatiens capensis Meerb. has only been studied in America, specifically in zones of the U.S.A. and Canada. In this study, we investigated the pollination biology of I. capensis using an integrative identification approach using morphological and molecular tools in four populations of Northwest Poland. We also determined and compared the functional characteristics of the pollinators of the introduced species from the study sites and the native ones reported, for the latter collecting information from bibliographic sources. Visitors were identified using standard morphological keys, including identifying and classifying insect mouthparts. Molecular identification was carried out using mitochondrial DNA's cytochrome oxidase subunit I (COI). We morphologically identified 20 species of visitors constituted by 17 pollinators and three nectar robbers. DNA barcoding of 59 individuals proved the identification of 18 species (also 18 BINs). The frequency of pollinator species was primarily made up of representatives of both Hymenoptera (75%) and Diptera (21%). The morphological traits, such as the chewing and sucking mouthparts, small and big body height, and robber and pollinator behavior explained mainly the native and introduced visitors' arrangements that allow pollination success. However, to understand the process comprehensively, further investigation of other causalities in pollination success and understanding the diversity of pollinators in outer native ranges are necessary.

Socioecological drivers of mutualistic and antagonistic plant-insect interactions and interaction outcomes in suburban landscapes.

Cities are complex socioecological systems, yet most urban ecology research does not include the influence of social processes on ecological outcomes. Much of the research that does address social processes focuses primarily on their effects on biotic community composition, with less attention paid to how social processes affect species interactions. Linking social processes to ecological outcomes is complicated by high spatial heterogeneity in cities and the potential for scale mismatch between social and ecological processes, and the indicators used to assess those processes. Here, we assessed how social and ecological processes jointly influence the frequency and outcomes of species interactions among the native perennial vine Gelsemium sempervirens and its insect pollinators, nectar robbers, and florivores across 28 residential subdivisions in the Research Triangle region, NC, USA. We integrated data on socioeconomic attributes (mean property value, mean property size, subdivision age), vegetation attributes (forest cover and richness and density of managed and unmanaged floral resources), species interactions (conspecific and heterospecific pollen deposition, nectar robbing, florivory), and Gelsemium reproduction (fruit set, seeds per fruit) using structural equation modeling to understand the causal links between socioeconomic attributes, vegetation attributes, and interaction frequency and outcome. Among socioeconomic attributes, property value was the strongest predictor of interaction frequency, having both direct and vegetation-mediated indirect effects on pollination and florivory. However, the effect of socioeconomic attributes on plant reproduction was small. Overall, we were able to explain only a small amount of the variation in any species interaction or reproduction measure. This may be due to the functional similarity of subdivisions, despite large variation in both socioeconomic and vegetation attributes, or may reflect scale mismatch between the ecological and socioeconomic variables. Our findings highlight the need to develop scale-appropriate indicators to improve our understanding of the links between social and ecological processes in urban landscapes.

Illegitimate flower visitors and pollinators are associated with different flower morphology: Evidence from five species of Penstemon (Plantaginaceae)

The role of pollinators as drivers of morphological diversification has been extensively documented. However, how non-pollinators, such as pollen thieves and nectar robbers, affect flower morphology has received little attention. In this study, we used five species of Penstemon to investigate the relationship between pollinators and non-pollinators, and the flower morphology of the plants they visit. The results suggest that smaller flowers are more likely to be predominantly visited by small and very small pollen-collecting bees, and that larger flowers are more likely to be visited by large bees. Very small and small pollen-collecting bees rarely contacted the stigma and can thus be characterized as illegitimate visitors. However, in the absence of a more efficient pollen vector, these visitors can act as occasional pollinators. On the other hand, nectar robbing by wasps was not correlated with flower size but was associated with premature wilting. Pollinator assemblages varied geographically, but the presence and frequency of non-pollinator visitors did not, and instead they were species-specific. Finally, our results suggest that non-pollinator visitors have a detrimental effect on flower appearance from the pollinators' perspective.

The conspicuously large bracts influence reproductive success in Thunia alba (Orchidaceae)

Abstract In angiosperms, diverse floral traits are adaptations to various selective pressures and ecological functions. So far, studies on floral traits in orchids have focused primarily on the labellum but never on bracts. A bumblebee-pollinated and rewarding terrestrial or epiphytic herb, Thunia alba (Lindley) H. G. Reichenbach (Orchidaceae), has conspicuously large and curly bracts that enclose the spur and pedicel of flowers. We hypothesized that these large bracts could protect spurs against nectar robbers. To confirm this hypothesis, we experimentally removed the bracts to record the changes in visiting behavior of mutualistic pollinators and antagonistic nectar robbers and evaluated their effects on reproduction success. Our result revealed that Bombus breviceps, the only pollinator of T. alba, shifted to nectar robbery when the bracts were removed, and the proportion of robbed flowers also significantly increased. Thunia alba was found to be pollinator limited regardless of whether in intact treatment or removed bract treatment. Removal of bracts had no effect on the visiting frequency of B. breviceps, but it reduced male and female reproductive success. These findings indicate that, under complex environmental pressures with limited pollination, large bracts can protect against nectar robbers and enhance the fitness of T. alba.

Nectar robbing by bees affects the reproductive fitness of the distylous plant Tirpitzia sinensis (Linaceae).

Nectar robbing can affect plant reproductive success directly by influencing female and male fitness, and indirectly by affecting pollinator behavior. Flowers have morphological and chemical features that may protect them from nectar robbers. Previous studies on nectar robbing have focused mainly on homotypic plants. It remains unclear how nectar robbing affects the reproductive success of distylous plants, and whether defense strategies of two morphs are different. Nectar-robbing rates on the long- and short-styled morph (L-morph, S-morph) of the distylous Tirpitzia sinensis were investigated. We compared floral traits, the temporal pattern of change in nectar volume and sugar concentration, nectar secondary metabolites, and sugar composition between robbed and unrobbed flowers of two morphs. We tested direct effects of nectar robbing on female and male components of plant fitness and indirect effects of nectar robbing via pollinators. Nectar-robbing rates did not differ between the two morphs. Flowers with smaller sepals and petals were more easily robbed. The floral tube diameter and thickness were greater in L-morphs than in S-morphs, and the nectar rob holes were significantly smaller in L-morphs than in S-morphs. Nectar robbing significantly decreased nectar replenishment rate but did not affect nectar sugar concentration or sugar composition. After robbery, the quantities and diversity of secondary compounds in the nectar of S-morphs increased significantly and total relative contents of secondary compounds in L-morphs showed no obvious changes. Nectar robbing could decrease female fitness by decreasing pollen germination rate and thus decreasing seed set. Nectar robbing had no significant effects on male fitness. Robbed flowers were less likely to be visited by hawkmoth pollinators, especially in S-morphs. These results suggest that nectar robbing could directly and indirectly decrease the female fitness of T. sinensis, and different morphs have evolved different defense mechanisms in response to nectar-robbing pressure.

Cheaters among pollinators: Nectar robbing and thieving vary spatiotemporally with floral traits in Afrotropical forests

AbstractNectar robbers and thieves are common antagonists in plant–pollinator communities, where they deplete nectar without pollinating flowers, substantially affecting plant reproduction. Nevertheless, little is known about the relative abundance of such nectar exploiters in communities, even though spatiotemporal changes in the frequencies of antagonists and mutualists can exert opposing selection pressures on the traits of the interacting species. Although these effects are highly dependent on the community context, interspecific interactions have almost exclusively been studied in interacting species pairs or single‐plant studies. We hypothesized that flowers might experience a trade‐off between filtering out robbers and thieves. We used an extensive dataset of video‐recorded flower–visitor interactions along a complete elevational gradient in wet and dry seasons on Mount Cameroon to assess spatiotemporal changes in robbing and thieving associated with several floral traits. Of the 14,391 recorded visits, ~4.3% were from robbers (mostly bees and birds) and ~2.1% were from thieves (mostly flies, bees, and moths). Only 29 and 39 of the 194 studied plants were robbed and thieved, respectively. We found that specialized floral traits that prevented thieving (such as long floral tubes or spurs) made flowers susceptible to robbing, and vice versa. Cheating behavior was most frequent at mid‐elevations, with more frequent robbing during the wet season and thieving during the dry season. These trends were linked to the local floral trait composition and the associations of cheating groups with specific floral traits. Our results suggest that the roles of antagonists and mutualists in shaping partner traits may vary across communities and that they deserve more attention in future studies of interspecific interactions.

Repeated Evolution of Unorthodox Feeding Styles Drives a Negative Correlation between Foot Size and Bill Length in Hummingbirds.

AbstractDifferences among hummingbird species in bill length and shape have rightly been viewed as adaptive in relation to the morphology of the flowers they visit for nectar. In this study we examine functional variation in a behaviorally related but neglected feature: hummingbird feet. We gathered records of hummingbirds clinging by their feet to feed legitimately as pollinators or illegitimately as nectar robbers-"unorthodox" feeding behaviors. We measured key features of bills and feet for 220 species of hummingbirds and compared the 66 known "clinger" species (covering virtually the entire scope of hummingbird body size) with the 144 presumed "non-clinger" species. Once the effects of phylogenetic signal, body size, and elevation above sea level are accounted for statistically, hummingbirds display a surprising but functionally interpretable negative correlation. Clingers with short bills and long hallux (hind-toe) claws have evolved-independently-more than 20 times and in every major clade. Their biomechanically enhanced feet allow them to save energy by clinging to feed legitimately on short-corolla flowers and by stealing nectar from long-corolla flowers. In contrast, long-billed species have shorter hallux claws, as plant species with long-corolla flowers enforce hovering to feed, simply by the way they present their flowers.

Bumblebees with big teeth: revising the subgenus Alpigenobombus with the good, the bad and the ugly of numts (Hymenoptera: Apidae)

The mountain bumblebees of the subgenus Alpigenobombus Skorikov, 1914, are uniquely distinctive because the females have enlarged mandibles with six large, evenly spaced teeth, which they use to bite holes in long-corolla flowers for nectar robbing. Recognition of species in this subgenus has been uncertain, with names used in various combinations. To revise the species, we examined COI-like barcodes for evidence of species’ gene coalescents using MrBayes and PTP and we compare the coalescent groups with morphological variation for integrative assessment. While we seek to include only orthologous barcodes (the ‘good’) and exclude all of the more strongly divergent barcode-like numts (the ‘bad’), for some nominal taxa only low-divergence numts could be obtained (the ‘ugly’). For taxa with no orthologous sequences available, using a minimum number of the lowest divergence numts did yield coalescent candidates for species that were consistent with morphologically diagnosable groups. These results agree in recognising 11 species within this subgenus, supporting: (1) recognising the widespread European Bombus mastrucatus Gerstaecker, 1869 stat. rev. as a species separate from the west Asian B. wurflenii Radoszkowski, 1860 s. str.; (2) the recently recognised B. rainai Williams, 2022, as a species separate from B. kashmirensis Friese, 1909, within the western Himalaya; (3) the recognition once again of B. sikkimi Friese, 1918 stat. rev. and B. validus Friese, 1905 stat. rev. as species separate from B. nobilis Friese, 1905 s. str. within the eastern Himalaya and Hengduan regions; (4) confirming the recognition of B. angustus Chiu, 1948, B. breviceps Smith, 1852 s. lat., B. genalis Friese, 1918, and B. grahami (Frison, 1933) as separate species within the Himalaya, China, and Southeast Asia; (5) recognising the conspecificity of the nominal taxa (not species) channicus Gribodo, 1892 (Southeast Asia) and dentatus Handlirsch, 1888 (Himalaya) as parts of the species B. breviceps s. lat. (southern and eastern China); and (6) recognising the conspecificity of the rare taxon beresovskii (Skorikov, 1933) syn. n. as part of the species B. grahami within China. Nectar robbing by bumblebees is reviewed briefly and prospects for future research discussed.

FIRST REPORT OF NECTAR ROBBING BY SWORD-BILLED HUMMINGBIRDS ENSIFERA ENSIFERA

A growing number of hummingbird species are known to practice nectar robbing. Hummingbirds that rob nectar tend to have short bills and to rob flowers with long, tubular corollas that prevent the birds from accessing nectar through its openings. We document that Sword-billed Hummingbirds Ensifera ensifera, which have the longest bills of any hummingbird species, are secondary nectar robbers on flowers of the red angel’s trumpet Brugmansia sanguinea, which have long tubular corollas and are regularly pollinated by Sword-billed Hummingbirds. When obtaining nectar through the floral opening of B. sanguinea, Sword-billed Hummingbirds' heads may be completely enveloped by the flower, severely limiting their vision. Sword-billed Hummingbirds might be at a lower risk of predation when they rob nectar than when they insert their heads into the floral opening. Thus, nectar robbing in this species might function to reduce predation risk, although we have no data to support this speculation.

A new species of the genus Onychopterocheilus Blüthgen, 1955 from the Altai Mountains, with the re-description and new records of the closely related O. kiritshenkoi (Kostylev, 1940) (Hymenoptera: Vespidae: Eumeninae).

Onychopterocheilus (Asiapterocheilus) proshchalykini Fateryga, sp. nov. is described from the Altai Republic (Russia). The new species is closely related to O. (A.) kiritshenkoi (Kostylev, 1940) but distinctly differs from it by the structure of the clypeus, the female vertex and scutellum, the male genitalia, as well as the coloration. In addition, O. proshchalykini has somewhat larger body size. Onychopterocheilus kiritshenkoi is re-described. Both species have the northernmost distribution among 13 currently recognized species of the Central Asian subgenus Asiapterocheilus. Onychopterocheilus chinensis Gusenleitner, 2005 is transferred to this subgenus from the nominotypical one. Onychopterocheilus kiritshenkoi is recorded from the Altai Republic for the first time; two new localities of this species from Mongolia are also reported. Females of O. kiritshenkoi were observed at flowers of two species of Fabaceae: Caragana bungei Ledeb. and Vicia costata Ledeb. The wasps acted as primary nectar robbers, i.e., they made holes in the calyx to access nectar with their relatively long proboscises.