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Cuticular hydrocarbons (CHCs) are waxy compounds on the surface of insects that prevent desiccation and frequently serve as chemical signals mediating social and mating behaviors. Although their function in eusocial species has been heavily investigated, little is known about the evolution of CHC-based communication in species with simpler forms of social organization lacking specialized castes. Here we investigate factors shaping CHC variation in the orchid bee Euglossa dilemma, which forms casteless social groups of two to three individuals. We first assess geographic variation, examining CHC profiles of males and females from three populations. We also consider CHC variation in the sister species, Euglossa viridissima, which occurs sympatrically with one population of E. dilemma. Next, we consider variation associated with female behavioral phases, to test the hypothesis that CHCs reflect ovary size and social dominance. We uncover a striking CHC polymorphism in E. dilemma spanning populations. In addition, we identify a separate set of CHCs that correlate with ovary size, social dominance, and expression of genes associated with social behavior, suggesting that CHCs convey reproductive and social information in E. dilemma. Together, our results reveal complex patterns of variation in which a subset of CHCs reflect the social and reproductive status of nestmates.

Male neotropical orchid bees (Euglossini) collect volatiles from varied sources in their environment to compile complex, species-specific tibial perfumes, which are later released at mating sites. ...

Abundance and diversity of bumblebees have been declining over the past decades. To successfully conserve bumblebee populations, we need to understand how landscape characteristics affect the quantity and quality of floral resources collected by colonies and subsequently colony performance. We therefore investigated how amount and composition of pollen collected by buff-tailed bumblebee Bombus terrestris colonies was affected by the surrounding landscape (i.e. the proportion of forest, urban, semi-natural habitats) and how they were related to colony growth. Thirty B. terrestris colonies were placed at grassland sites differing in surrounding landscape. Colonies were established in spring when availability of flowering plants was highest, and their weight gain was monitored for 1 month. We additionally recorded the quantity and compared plant taxonomic composition and nutritional quality (i.e. amino acid composition) of pollen stored. Bumblebee colonies varied little in the pollen spectra collected despite differences in surrounding landscape composition. They collected on average 80 % of pollen from woody plants, with 34 % belonging to the genus Acer. Early colony growth positively correlated with total amount of woody pollen and protein collected and decreased with increasing proportions of semi-natural habitats and total amino acid concentrations. Our results suggest that woody plant species represent highly important pollen sources for the generalist forager B. terrestris early in the season. We further show that colony growth of B. terrestris is predominantly affected by the quantity, not quality, of forage, indicating that several abundant plant species flowering throughout the bumblebees’ foraging season may cover the colonies’ nutritional needs.

Insects rely on the olfactory system to detect a vast diversity of airborne molecules in their environment. Highly sensitive olfactory tuning is expected to evolve when detection of a particular chemical with great precision is required in the context of foraging and/or finding mates. Male neotropical orchid bees (Euglossini) collect odoriferous substances from multiple sources, store them in specialized tibial pouches and later expose them at display sites, presumably as mating signals to females. Previous analysis of tibial compounds among sympatric species revealed substantial chemical disparity in chemical composition among lineages with outstanding divergence between closely related species. Here, we tested whether specific perfume phenotypes coevolve with matching olfactory adaptations in male orchid bees to facilitate the location and harvest of species-specific perfume compounds. We conducted electroantennographic (EAG) measurements on males of 15 sympatric species in the genus Euglossa that were stimulated with 18 compounds present in variable proportions in male hind tibiae. Antennal response profiles were species-specific across all 15 species, but there was no conspicuous differentiation between closely related species. Instead, we found that the observed variation in EAG activity follows a Brownian motion model of trait evolution, where the probability of differentiation increases proportionally with lineage divergence time. However, we identified strong antennal responses for some chemicals that are present as major compounds in the perfume of the same species, thus suggesting that sensory specialization has occurred within multiple lineages. This sensory specialization was particularly apparent for semi-volatile molecules (‘base note’ compounds), thus supporting the idea that such compounds play an important role in chemical signaling of euglossine bees. Overall, our study found no close correspondence between antennal responses and behavioral preferences/tibial contents, but confirms the utility of EAG profiling for discovering certain behaviorally active compounds.

Male Neotropical orchid bees collect volatile chemicals from their environment and compose species-specific volatile signals, which are subsequently exposed during courtship display. These perfumes are hypothesized to serve as attractants and may play a role in female mate choice. Here, we investigated the potential of cuticular hydrocarbons as additional recognition cues. The cuticular hydrocarbons of males of 35 species belonging to four of the five extant euglossine bee genera consisted of aliphatic hydrocarbons ranging in chain lengths between 21 and 37 C-atoms in distinct compositions, especially between sympatric species of similar coloring and size, for all but one case. Cleptoparasitic Exaerete spp. had divergent profiles, with major compounds predominantly constituted by longer hydrocarbon chains (>30 C-atoms), which may represent an adaptation to the parasitic life history ("chemical insignificance"). Phylogenetic comparative analyses imply that the chemical profiles exhibited by Exaerete spp. are evolutionarily divergent from the rest of the group. Female hydrocarbon profiles were not identical to male profiles in the investigated species, with either partial or complete separation between sexes in multivariate analyses. Sexually dimorphic hydrocarbon profiles are assumed to be the basis for sex recognition in a number of insects, and thus may supplement the acquired perfume phenotypes in chemical information transfer. Overall, cuticular hydrocarbons meet the requirements to function as intraspecific and intersexual close range recognition signals; behavioral experiments are needed to determine their potential involvement in mate recognition.

Male neotropical orchid bees collect volatile substances from their environment and compose complex, species-specific odour blends in leg pouches. These perfumes are accumulated by the males over time and are exposed during pre-mating display. It has been hypothesized that perfumes are indicators of male genotypic quality and that females chose mates by the quality or intensity of their odour. Because direct experimental proof is lacking, we investigated whether the amount or complexity of male perfumes is related to male (1) size, (2) fluctuating (left–right) asymmetry, or (3) age, traits that are known to be sexually selected in other animals. We measured left and right forewings (cell node distances for 1 and 2, wing wear for 3) of Euglossa dilemma and Euglossa viridissima collected during dry and rainy seasons on the Yucatan peninsula, Mexico (total N = 768). Wing size was not related to the quantity or the complexity of perfume extracts in either species after excluding the effect of season, which positively affected both size and perfume load in E. dilemma. Wing asymmetry had also no effect, except in rainy season E. viridissima, where it was positively (not negatively) correlated with the quantity of perfume. Wing wear, an established age indicator of orchid bees, had the only consistent overall effect, being positively correlated with perfume amount and complexity in both species. This is in agreement with the idea that perfumes are an honest indicator of male survival capacity.

The mating system of European wool-carder bees, Anthidium manicatum, differs from that of most bees in three important aspects: females (1) are polyandrous and (2) mate continuously over the course of their reproductive life, while males (3) exhibit resource defence polygyny, that is, defend patches of food plants where copulations occur. To shed light on the evolution of this mating system we investigated male paternity using a combination of cage experiments and microsatellite genotyping of brood. We found that, although females possess a spermatheca for long-term sperm storage, most brood was fathered by males that had very recently mated with the breeding female, indicating pronounced last (or at least ‘late’) male sperm precedence. In the absence of males (male exclusion experiment) a large proportion of eggs remained unfertilized (resulting in haploid male offspring), but some diploid daughters arose from fathers that had been removed at least 11 days prior to egg laying. It appears that most A. manicatum eggs are fertilized with sperm from the bursa copulatrix, while the spermatheca serves only as a backup reservoir. This is the first demonstration of last male sperm precedence in aculeate Hymenoptera (bees, wasps, ants). We suggest that it has coevolved with ‘resource defence’ or

Social parasites can break into their host colonies using sensory deception, force, or both. To evaluate the role of sensory deception in eusocial obligate food robbers, we studied the Mesoamerican stingless bee Lestrimelitta niitkib –host species system, including preferred and nonpreferred host species. The use of citral as a propaganda substance is documented in L. niitkib , but possible mechanisms used by individual scouts to overcome host species recognition have not been studied. We analysed the cuticular profiles of L. niitkib and host species, coupled with bioassays of time to aggression (latency) and included data on host species raid frequency. We found that L. niitkib has a simple, but not insignificant, cuticular profile. Generally, L. niitkib cuticular profiles were similar to (but did not mimic) profiles of its preferred host species and differed from profiles of nonpreferred hosts. As expected, latency generally fitted a recognition system based on the degree of similarity between the cleptobiont's cuticular label and the host species template, with chemically similar species reacting slower and chemically distant species reacting rapidly to L. niitkib . There was a positive correlation between raid ratio and latency, indicating that the speed of detection and aggression towards L. niitkib scouts could influence host species selection. Cuticular profile similarity of individual L. niitkib scouts to host species may help L. niitkib scouts evade recognition and attacks from guards. In a further step, unnoticed L. niitkib scouts could successfully recruit nestmates to mass-raid host species colonies. The fact that L. niitkib can also plunder aggressive species, suggests that obligate cleptobiosis within its narrow biological niche could be characterized by flexibility in invasion strategies to allow exploiting a broad range of host species and be successful over evolutionary times.

In orchid bees, males signal their availability as mates by fanning ‘perfumes’, i.e. blends of volatiles that are collected from environmental sources and stored in hind leg pouches. The chemical composition of such perfumes in males with either two or three mandibular teeth has previously led to the discovery of two sympatric, cryptic lineages within Euglossa viridissima Friese on the Yucatan peninsula, Mexico. Here, we combine chemical, morphological, and genetic data for an integrated characterization of the two lineages. The lectotype of E. viridissima Friese in the Museum of Natural History in Vienna has two mandibular teeth, and the species name viridissima must thus be assigned to the predominantly bidentate lineage, whereas the completely tridentate lineage is described as a novel species, Euglossa dilemma sp. nov. Bembe & Eltz. Chemical profiling and microsatellite genotyping revealed that E. viridissima males can occasionally (∼10% of individuals) express a third mandibular tooth, but this tooth is not positioned centrally on the mandible as in E. dilemma, but is displaced towards the tip. Thus, males of the two lineages can be unambiguously diagnosed by mandibular characters alone. Based on 889 bp of CO1 sequence data, we confirm that E. viridissima and E. dilemma constitute a monophyletic group within the genus Euglossa. However, CO1 alone failed to separate these two lineages due to the lack of parsimony-informative sites. Both species occur in broad sympatry across Central America, but the orchid bees recently introduced to Florida have three mandibular teeth in males, i.e. belong to E. dilemma. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, 1064–1076.

Habitat degradation and fragmentation are widespread phenomena in tropical regions. Negative effects on the biota are numerous, ranging from interruption of gene flow among populations, to the loss of genetic diversity within populations, to a decline in species richness over time. Orchid bees (Hymenoptera: Apidae: Euglossini) are of major conservation interest due to their function as pollinators of numerous orchid species and other tropical plants. Here, we used microsatellite markers to investigate the effects of geographic distance and habitat fragmentation on gene flow among populations. Populations of Euglossa dilemma in three geographic regions—the Yucatan peninsula (Mexico), Veracruz (Mexico), and Florida (USA)—were genetically structured predominantly across the regions, with the strength of differentiation among populations being positively correlated with geographic distance. Within geographic regions only little substructure was found, suggesting that dispersal is substantial in the absence of geographic or ecological barriers. In a second study, patterns of genetic differentiation among eight species of Euglossa were not related to habitat fragmentation following deforestation in southern Mexico (Veracruz). Specifically, most bee populations in the 9,800 ha forest remnant of Los Tuxtlas (Volcano San Martin) were neither differentiated from, nor had less genetic diversity than, populations in near-continuous forest separated from Los Tuxtlas by 130 km of agricultural land. Either occasional long distance dispersal across open areas has buffered the expected genetic effects of fragmentation, or the history of fragmentation in southern Mexico is too recent to have caused measurable shifts in allelic composition.

SUMMARY That hummingbird-pollinated plants predominantly have red flowers has been known for decades, but well-investigated research studies are still rare. Preference tests have shown that hummingbirds do not have an innate preference for red colours. In addition, hummingbirds do not depend solely upon red flowers, because white-flowered hummingbird-pollinated plants are also common and temporarily abundant. Here we show that both white and red hummingbird-pollinated flowers differ from bee-pollinated flowers in their reflection properties for ultraviolet (UV) light. Hummingbird-pollinated red flowers are on average less UV reflective, and white hummingbird-pollinated flowers are more UV reflective than the same coloured bee-pollinated ones. In preference tests with artificial flowers, neotropical orchid bees prefer red UV-reflecting artificial flowers and white UV-nonreflecting flowers over red and white flowers with the opposite UV properties. By contrast, hummingbirds showed no preference for any colour in the same tests. Plotting floral colours and test stimuli into the honeybees' perceptual colour space suggests that the less attractive colours are achromatic for bees and therefore more difficult to detect against the background. This underlying colour preference in bees might provide hummingbirds with a private niche that is not attractive to bees.

Male orchid bees collect volatiles, from both floral and non-floral sources, that they expose as pheromone analogues (perfumes) during courtship display. The chemical profile of these perfumes, which includes terpenes and aromatic compounds, is both species-specific and divergent among closely related lineages. Thus, fragrance composition is thought to play an important role in prezygotic reproductive isolation in euglossine bees. However, because orchid bees acquire fragrances entirely from exogenous sources, the chemical composition of male perfumes is prone to variation due to environmental heterogeneity across habitats. We used Gas Chromatography/Mass Spectrometry (GC/MS) to characterize the perfumes of 114 individuals of the green orchid bee (Euglossa aff. viridissima) sampled from five native populations in Mesoamerica and two naturalized populations in the southeastern United States. We recorded a total of 292 fragrance compounds from hind-leg extracts, and found that overall perfume composition was different for each population. We detected a pronounced chemical dissimilarity between native (Mesoamerica) and naturalized (U.S.) populations that was driven both by proportional differences of common compounds as well as the presence of a few chemicals unique to each population group. Despite these differences, our data also revealed remarkable qualitative consistency in the presence of several major fragrance compounds across distant populations from dissimilar habitats. In addition, we demonstrate that naturalized bees are attracted to and collect large quantities of triclopyr 2-butoxyethyl ester, the active ingredient of several commercially available herbicides. By comparing incidence values and consistency indices across populations, we identify putative functional compounds that may play an important role in courtship signaling in this species of orchid bee. Electronic supplementary material The online version of this article (doi:10.1007/s10886-010-9821-3) contains supplementary material, which is available to authorized users.

Male Neotropical orchid bees (Euglossini) collect volatile substances (fragrances) from flowers and other sources (e.g., decaying wood) and store them in specialized hind tibial pockets. The accumulated chemicals are later emitted during courtship display, presumably to lure conspecific females for mating. We analyzed tibial fragrances of males of 15 sympatric Panamanian species in the genus Euglossa to test whether communities of euglossine bees are chemically structured, and to elucidate whether male fragrance signals evolve to convey premating isolation. Our analysis revealed substantial chemical disparity among all lineages. Disparity was mediated by compounds that were exclusive to certain species but also by differences in relative quantity of shared compounds. We mapped tibial fragrance compounds present in each species on a DNA-based phylogeny (reconstructed using partial sequences of COI, EF1-alpha, ArgK, and Pol-II) and found that most dominant compounds were highly homoplasious. In an analysis of chemical differentiation in relation to phylogenetic divergence through time, disparity was greater than expected from a null model at any point during evolutionary history, suggesting that diversifying selection has shaped fragrance phenotypes. Notably, chemical disparity was greater within recently diverged lineages than among them, suggesting that chemical preferences in orchid bees evolved rapidly in the early stages of species divergence. We postulate communication interference as the possible mechanism behind the observed fragrance differentiation, which may be the product of reproductive character (fragrance) displacement. Our findings are consistent with the hypothesis that male fragrance signals evolve to convey premating isolation.

We compared nectar, pollen and resin loads of individual workers among colonies from six Trigona species in Sabah, Borneo. Individual bees rarely collected large amounts of both nectar and pollen during the same foraging trip. Instead, comparison of crop contents across departing, flower-visiting, and returning bees suggests that pollen-collecting workers often carried highly concentrated nectar in their crop upon nest departure. During their foraging trip, this crop nectar volume decreased progressively until crops were largely empty when they returned to their nest. Individually marked pollen foragers carried highly concentrated nectar when they left their nest, while crops and corbiculae from marked nectar foragers were empty upon departure. We suggest that a large proportion of previously stored and highly concentrated nectar may be required for pollen adhesion to corbiculae and/or serve as fuel during foraging on nectar-poor flowers.

Male orchid bees (Euglossini) collect fragrances from flowers and other natural sources, a behaviour that has shaped the euglossine pollination syndrome. Males store such chemicals in hind leg pouches and later expose them during courtship display. In the present study, we show that complex bouquets of two sympatric species of Eulaema, E. meriana and E. bombiformis, are chemically distinct. When exposed during bioassays at display perches individual hind leg extracts rapidly and consistently attracted other males of the correct species, even if derived from males of disparate localities (French Guiana and Panama). Conspecific males as well as females of E. bombiformis arrived at natural perch sites only from downwind, and two copulations were observed. Our findings demonstrate that acquired odours mediate exclusive attraction within species and support the idea that such fragrances are pheromone analogues. Their role in acquiring matings and during male-male interaction is discussed.

Many insects are known to leave lipid footprints while walking on smooth surfaces. Presumably, the deposited substances improve tarsal adhesion. In bumblebees, footprint hydrocarbons also function as scent marks that allow detection and avoidance of recently depleted flowers. I used GC-MS to detect hydrocarbons deposited by bumblebee (Bombus pascuorum) on flowers of Lamium maculatum. In addition to the plants' own cuticular lipids, extracts of corollas that had been visited by bumblebees contained odd-numbered alkenes. The amount of pentacosenes (C25H50) on corollas was linearly related to the number of bumblebee visits, with workers depositing approximately 16 ng per visit (extrapolated to a total of 65 ng of bumblebee cuticular hydrocarbons). Pentacosenes were retained on visited flowers without loss for 2 hr, and probably longer. This and results from flight cage experiments suggest that flower epicuticles retain a chemical record of pollinator visitation, including information on visiting bee species. Continuous footprint accumulation necessitates new explanations concerning the reversibility of "repellent scent marks" of bumblebees.

Male neotropical orchid bees (Euglossini) collect odoriferous substances from orchids and other sources and store them in tibial pouches, accumulating complex and species-specific bouquets. These fragrances are later exposed at display sites, presumably to attract females or conspecific males or both. We hypothesized that the necessity to detect and recognize specific fragrance bouquets has led to peripheral chemosensory specializations in different species of orchid bees. To test this, excised male antennae of four species of Euglossa were stimulated with complete tibial extracts of the same four species in a crosswise experiment. In the majority of the tested extracts, the amplitude of the electroantennogram (EAG) response was significantly different between species and always maximal in males of the extracted species. This effect did not appear to result from a given species' increased sensitivity toward certain attractive components: gas chromatography with electroantennographic detection (GC-EAD) of one extract of Euglossa tridentata evoked similar and generalized response patterns in all four species, encompassing a total of 34 peaks that elicited antennal responses. Therefore, the species effect in EAG responses to complete extracts likely resulted from species-specific interactions of compounds at the receptor level. Antennal specialization to conspecific bouquets adds additional strength to the argument that specificity is an important evolutionary aspect of euglossine tibial fragrances.

Male orchid bees (Euglossini) are attracted to floral and non-floral odours, which they collect and accumulate in hind tibial cavities for subsequent exposure during courtship. Fragrance preferences are species-specific, leading to relatively specialised pollination of euglossophilous plants. We tested the hypothesis that preferences for attractive compounds have led to species-specific sensory adaptations that are measurable by electroantennography (EAG). All of 16 synthetic fragrance compounds elicited significant responses on male bee antennae, with some difference of response spectra between individuals of Euglossa spp. and bumblebee (Bombus terrestris) controls, but no difference between three different species of Euglossa. There was no correspondence between a compounds’ attractiveness in baiting assays and the size of its electrophysiological response. Our results strengthen the view that fragrance preferences are largely mediated by processes in higher nervous centres. Peripheral sensory tuning to single attractive odorants may be constrained by the need to detect and discriminate between many fragrances, including many that have repellent effects on male bees.

The abundance and species richness of highly social bees (Apinae: Meliponini, Apini) were studied at 12 dipterocarp forest sites in Sabah, northern Borneo, using standardized honey-water baiting assays. The 12 sites were grouped in five localities varying in the degree and history of disturbance from selective logging. A baiting assay consisted of spraying diluted honey on vegetation along transects and recording bee arrival on the same day. Repeated assays of the same sites were run in two consecutive years, 1998 and 1999. One-way repeated-measures ANOVAs were calculated on bee abundance and species richness, with locality and year as independent factors. There were significant or marginally significant effects of forest locality on all measures of bee abundance and species richness. However, there were also significant interactions between year and locality on these variables, thwarting conclusions on the effects of logging on bee communities. The diverging results of the two years are likely related to spatio-temporal variation of flowering activity prior to and during the assays, with between-year differences being amplified by pronounced differences in climatic conditions (ENSO). Local or regional differences in flowering phenology complicate the application of resource-based baiting techniques for between-site comparisons of bee diversity.

Nesting habits of highly social stingless bees (Meliponini) were studied in lowland dipterocarp forests in Sabah, Borneo. A total of 275 nests of 12 species of bees were located. All nests were closely associated with living (91.5%) or dead (8.5%) trees, either within pre-formed cavities in the trunk (cavity nests) or situated in or under the tree base (base nests). Species of bees differed in nesting habit. The majority of species (seven) were cavity nesters, but the majority of nests (81%) were base nests. Nests were often aggregated (mean of 1.94 nests/nest tree), with up to eight colonies and three species in a single tree. Nest trees were mostly large to very large (86.1% above 60 cm dbh) commercial timber trees; 47.3% of nest trees were dipterocarps. According to visual inspection nest trees were of significantly lower expected timber quality then randomly chosen control trees. Taking into account information on tree species, size and expected timber quality, we estimated that 34.0 or 42.6% of nest trees were potential harvest trees, depending on harvesting regulations (reduced impact logging (RIL) versus conventional). Lower percentages under RIL guidelines were mostly due to size restrictions that protect very large trees (>120 cm dbh). Harvesting is likely to kill bee colonies associated with the respective tree. Therefore, and because meliponine colonies are long-lived and have low fecundity, direct impact from logging may have lasting effects on bee populations. Harvesting guidelines that retain high proportions of large and hollow trees should be promoted in order to preserve meliponine pollination in sustainable forest management.

We measured the nest density of stingless bees (Apidae, Meliponini) in undisturbed and logged-over dipterocarp forests in Sabah, northern Borneo, and eval- uated hypotheses on proximate factors leading to the ob- served variation: population control mediated by (1) nest predation, (2) limitation of nest trees, or (3) food limita- tion. Per-area nest density varied twentyfold across 14 forest sites and was significantly affected by locality, but not by the degree and history of disturbance. Nest densi- ty was generally high in sites located in the Sepilok For- est fragment (mean 8.4 nests/ha), bordering mangroves or plantations. In contrast, nest densities in continu- ous forests were all low (between 0 and 2.1 nests/ha, mean 0.5 nests/ha). Yearly nest mortality was low (13.5-15.0%) over 4 years of observation and did not vary between forest localities, thus limiting the potential of nest predation (1) in creating the observed variation in nest density. The presence of potential nest trees (2), though positively correlated with nest density, explained only a minute fraction of the observed variation. Nest density was best explained by differences in the pollen resources (3) available to the bees (quantified by analy- sis of pollen in bee garbage). Across five selected sites the amount of nonforest pollen (from mangrove or crop plants) included in diets of Trigona collina was positive- ly correlated with T. collina nest density. External pollen sources are a likely supplement to bee diets at times when little flowering occurs inside the forest, thus in- creasing overall bee carrying capacity. Pollen limitation was also indicated by direct measurements of pollen im- port and foraging activity of T. collina in three selected sites: Pollen traps installed at nests in high-density Sep- ilok captured significantly more corbicular pollen than colonies in low-density Deramakot. At the same time, morning foraging activity was also greater in Sepilok, in- dicating a regulatory increase in foraging in response to high pollen availability. We conclude that the abundance of stingless bees in forests in Sabah is chiefly dependent on the local availability of food resources. Bee popula- tions strongly benefit from edge effects and increased foraging habitat diversity. Electronic supplementary ma- terial to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00442- 001-0848-6

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.

The relative effects of foraging benefits (food intake) and costs (disturbance = pit destruction) on growth rate and foraging behavior of larvae of the ant-lionMyrmeleon mobilis were investigated. In a laboratory experiment second-instar larvae were subjected to combinations of three rates of feeding and three rates of disturbance. Pit relocations were generally rare but occurred more often in starved larvae. Disturbance rate had no significant effect on pit relocation rate. Feeding rate was a major determinant of the energy allocated in pit construction and maintenance (positive relationship). In a second experiment third-instar larvae encountered changing rates of disturbance. Pit size was reduced as a response to increased rates of disturbance. Disturbance had no detectable effect on growth. In general,M. mobilis larvae were cost-conservative, foragers.

In the course of a study on pollen diets of three sympatric species of stingless bees (Apidae: Meliponini) in Sabah, Malaysia, we made the observation that large fractions of the foragers of three colonies of Trigona collina collected corbicular loads of fungal spores in lieu of pollen. Collection of spores continued for at least three consecutive days. The spores were brought to germination in the laboratory and the culture was identified as mold of the genus Rhizopus (Zygomycota, Mucorales). Our observations represent the first reported case of the collection of Rhizopus mold spores in lieu of pollen by bees and a rare case of the collection of fungal spores by bees other than honeybees (Apis).

Male neotropical orchid bees (Euglossini) collect volatile chemicals from their environment, store them in tibial pouches, and later expose their "perfumes" during a courtship display. Here, we showed that enantiomeric selectivity plays an important role in the choice of volatiles by male Euglossa cyanura in southern Mexico, and that behavioral selectivity is linked to antennal sensitivity. In field bioassays with equal concentrations of (+)-ipsdienol, (-)-ipsdienol, and racemate, males preferred the (-)-isomer to the racemate, while neglecting the (+)-isomer. Correspondingly, antennae of male E. cyanura showed larger electroantennographic responses to the (-)-isomer than to the (+)-isomer. In comparison, antennae of male Euglossa mixta, which are not attracted to any form of ipsdienol, showed lower electroantennographic responses to (-)-ipsdienol than did antennae of E. cyanura, and also did not differ in sensitivity with respect to the (+)- or (-)-isomers. We suggest that (-)-ipsdienol is an important component of perfume signals in male E. cyanura, which have undergone selection in favor of increased antennal sensitivity to that enantiomer.

Allozyme analyses have suggested that Neotropical orchid bee (Euglossini) pollinators are vulnerable because of putative high frequencies of diploid males, a result of loss of sex allele diversity in small hymenopteran populations with single locus complementary sex determination. Our analysis of 1010 males from 27 species of euglossine bees sampled across the Neotropics at 2–11 polymorphic microsatellite loci revealed only five diploid males at an overall frequency of 0.005 (95% CIs 0.002–0.010); errors through genetic nondetection of diploid males were likely small. In contrast to allozyme-based studies, we detected very weak or insignificant population genetic structure, even for a pair of populations >500 km apart, possibly accounting for low diploid male frequencies. Technical flaws in previous allozyme-based analyses have probably led to considerable overestimation of diploid male production in orchid bees. Other factors may have a more immediate impact on population persistence than the genetic load imposed by diploid males on these important Neotropical pollinators.