Born to be bee, fed to be worker? The caste system of a primitively eusocial insect.

ABSTRACT: INTRODUCTION: Primitively eusocial halictid bees are excellent systems to study the origin of eusociality, because all individuals have retained the ancestral ability to breed independently. In the sweat bee Halictus scabiosae, foundresses overwinter, establish nests and rear a first brood by mass-provisioning each offspring with pollen and nectar. The mothers may thus manipulate the phenotype of their offspring by restricting their food provisions. The first brood females generally help their mother to rear a second brood of males and gynes that become foundresses. However, the first brood females may also reproduce in their maternal or in other nests, or possibly enter early diapause. Here, we examined if the behavioural specialization of the first and second brood females was associated with between-brood differences in body size, energetic reserves and pollen provisions. RESULTS: The patterns of variation in adult body size, weight, fat content and food provisioned to the first and second brood indicate that H. scabiosae has dimorphic females. The first-brood females were significantly smaller, lighter and had lower fat reserves than the second-brood females and foundresses. The first-brood females were also less variable in size and fat content, and developed on homogeneously smaller pollen provisions. Foundresses were larger than gynes of the previous year, suggesting that small females were less likely to survive the winter. CONCLUSIONS: The marked size dimorphism between females produced in the first and second brood and the consistently smaller pollen provisions provided to the first brood suggest that the first brood females are channelled into a helper role during their pre-imaginal development. As a large body size is needed for successful hibernation, the mother may promote helping in her first brood offspring by restricting their food provisions. This pattern supports the hypothesis that parental manipulation may contribute to promote worker behaviour in primitively eusocial halictids.

Females of Tapinotaspoides, a genus in the oil-collecting bee tribe Tapinotaspidini, collect secretions from non-floral trichomes (Hymenoptera, Apidae)

Harvesting of secretions from non-floral trichomes by females of Tapinotaspoides serraticornis is reported for the first time. The females exhibit a type of mopping behavior using the fringes of long, wavy setae along the posterior margins of their metasomal sterna. Our observations indicated a wide range of host plants used as sources for these secretions, including Waltheria (Sterculiaceae), Tibouchina (Melastomataceae), Sida (Malvaceae), Jacquemontia (Convolvulaceae), and unidentified species of Commelinaceae and Cyperaceae.

Structure of bee-flower system in the coastal sand dune of Abaeté, northeastern Brazil

For twelve months (from January to December of 1996) we investigated bee-flower interactions in a sea coastal ecosystem in Bahia, Brazil. Samples were taken three times each month. 3983 individuals belonging to 49 bee species, grouped in 13 morph-functional categories, visited 66 plant species belonging to 39 botanic families. It was observed 310 interactions between bees and plants at species level. The use of floral resources by bees was not homogeneous; most of the plant species received a low number of visitors. No restricted plant-bee species relationship in resource use concerning the subset of analyzed interactions was detected. In Abaeté the generalist relationships predominated.

Revision of the New World bee fly genus Heterostylum Macquart (Diptera, Bombyliidae, Bombyliinae)

The genus Heterostylum Macquart and five Neotropical species (H. ferrugineum (Fabricius, 1805), H. hirsutum (Thunberg, 1827), H. rufum (Olivier, 1789), H. haemorrhoicum (Loew, 1863) and H. pallipes Bigot, 1892) are redescribed. The other species, recently redescribed or described are only diagnosed, except for H. deani Painter, 1930, whose spermathecae are described and illustrated for the first time. The main characters of the external morphology were photographed and the male genitalia and female spermathecae illustrated. An identification key to all included species is also presented.

New enigmatic Andean bee species of Protandrena (Hymenoptera, Andrenidae, Panurginae)

Panurgine bees are diverse and abundant in temperate areas of the Americas but poorly represented to nearly absent in the tropics. We describe and illustrate five distinctive new species of the genus Protandrena that occur at high altitudes (2000-3400 m) in the Andes, from Venezuela to Ecuador. The species are also described to make the names available in forthcoming papers on their biology. These Andean species resemble some members of the subgenus Heterosarus but differ from it, as well as from any other subgenera of Protandrena, primarily in characters of the male genitalia and hidden sterna. The South American Protandrena s. l. are morphologically highly diverse and a complete study of the group is needed before supraspecific names are proposed for unusual species. Thus, to avoid further nomenclatural changes, we decided not to place these species in a new subgenus or any of the available subgenera. We also provide notes on the biology for some of the species.

Notes on oil sources for the bee genus Caenonomada(Hymenoptera, Apidae, Tapinotaspidini)

It is reported for the first time oil collecting by bees of the genus Caenonomada on flowers of Plantaginaceae. Females of Caenonomada unicalcarata were observed collecting oil on flowers of Angelonia cornigera, and males and females of Caenonomada bruneri and C. aff. unicalcarata were observed on flowers of Angelonia and Monopera (Plantaginaceae). The record of Caenonomada on Plantaginaceae suggests the use of trichomatic oil glands as a primitive condition in the tribe Tapinotaspidini.

Flexible social organization and high incidence of drifting in the sweat bee, Halictus scabiosae.

The very diverse social systems of sweat bees make them interesting models to study social evolution. Here we focus on the dispersal behaviour and social organization of Halictus scabiosae, a common yet poorly known species of Europe. By combining field observations and genetic data, we show that females have multiple reproductive strategies, which generates a large diversity in the social structure of nests. A detailed microsatellite analysis of 60 nests revealed that 55% of the nests contained the offspring of a single female, whereas the rest had more complex social structures, with three clear cases of multiple females reproducing in the same nest and frequent occurrence of unrelated individuals. Drifting among nests was surprisingly common, as 16% of the 122 nests in the overall sample and 44% of the nests with complex social structure contained females that had genotypes consistent with being full-sisters of females sampled in other nests of the population. Drifters originated from nests with an above-average productivity and were unrelated to their nestmates, suggesting that drifting might be a strategy to avoid competition among related females. The sex-specific comparison of genetic differentiation indicated that dispersal was male-biased, which would reinforce local resource competition among females. The pattern of genetic differentiation among populations was consistent with a dynamic process of patch colonization and extinction, as expected from the unstable, anthropogenic habitat of this species. Overall, our data show that H. scabiosae varies greatly in dispersal behaviour and social organization. The surprisingly high frequency of drifters echoes recent findings in wasps and bees, calling for further investigation of the adaptive basis of drifting in the social insects.

Seasonal flight and resource collection patterns of colonies of the stingless bee Melipona bicolor schencki Gribodo (Apidae, Meliponini) in an Araucaria forest area in southern Brazil

Melipona bicolor schencki occurs in southern Brazil and at high elevations in southeastern Brazil. It has potential for use in meliponiculture but this stingless bee species is vulnerable to extinction and we have little knowledge about its ecology. In order to gather essential information for species conservation and management, we made a study of seasonal flight activities in its natural environment. We sampled bees entering the nests with pollen, nectar/water and resin/mud, in five colonies during each season. In parallel, we analyzed the influence of hour of the day and meteorological factors on flight activity. Flights were most intense during spring and summer, with daily mean estimates of 2,100 and 2,333 flights respectively, while in fall and winter the daily flight estimate was reduced to 612 and 1,104 flights, respectively. Nectar and water were the most frequently-collected resources, followed by pollen and building materials. This preference occurred in all seasons, but with variations in intensity. During spring, daily flight activity lasted over 14 hours; this period was reduced in the other seasons, reaching eight hours in winter. Meteorological factors were associated with 40.2% of the variation in flight and resource collection activity. Apparently, other factors that we did not measure, such as colony needs and availability of floral resources, also strongly influence the intensity of resource collection.

Diversity of the euglossine bee community (Hymenoptera, Apidae) of an Atlantic Forest remnant in southeastern Brazil

Diversity of the euglossine bee community (Hymenoptera, Apidae) of an Atlantic Forest remnant in southeastern Brazil. Euglossine bees, attracted to scent baits of cineole, eugenol and vanillin, were collected with entomological nets, from December 1998 to November 1999. Samplings were carried out once a month simultaneously by two collectors positioned in two different sites in an Atlantic Forest remnant in northeastern São Paulo state, Brazil. A total of 859 male euglossine bees, belonging to 13 species and four Euglossini genera were collected. Of the total sample, 506 (12 species) males were captured at site A and 353 (10 species) were collected at site B.In both sites, Euglossa pleosticta Dressler, 1982 was the most abundant species (45.79%), followed by Eulaema nigrita Lepeletier, 1841 (20.79%). The results of this study supply new information about the diversity of orchid bee fauna in Atlantic Forest remnants as well as show that more than one site is needed to sample these bees in a fragmented landascape.

Phylogeny and revision of the bee genus Rhinocorynura Schrottky (Hymenoptera, Apidae, Augochlorini), with comments on its female cephalic polymorphism

Phylogeny and revision of the bee genus Rhinocorynura Schrottky (Hymenoptera, Apidae, Augochlorini), with comments on its female cephalic polymorphism. A taxonomic revision and a phylogeny for the species of Rhinocorynura are provided. Six species are recognized: R. briseis, R. crotonis, R. inflaticeps and R. vernoniae stat. nov., the latter removed from synonymy with R. inflaticeps, in addition to two newly described species, R. brunnea sp. nov. and R. viridis sp. nov. Lectotypes for Halictus crotonis Ducke, 1906 and Halictus inflaticeps Ducke, 1906 are hereby designated. Another available name included in Rhinocorynura, Corynuropsis ashmeadi Schrottky, 1909, is removed from the genus and treated as species inquerenda in Augochlorini. Rhinocorynura is monophyletic in the phylogenetic analysis and the following relationships were found among its species: (R. crotonis (R. briseis ((R. brunnea sp. nov. + R. viridis sp. nov.) (R. inflaticeps + R. vernoniae)))). Biogeographic relationships within the genus and comparisons with related taxa are presented. Females of all species exhibit pronounced variation in body size, in two of them, R. inflaticeps and R. vernoniae, with structural modifications possibly linked to division of labor. Identification key and illustrations for the species are provided.

Effect of Citrus floral extracts on the foraging behavior of the stingless bee Scaptotrigona pectoralis (Dalla Torre)

Effect of Citrus floral extracts on the foraging behavior of the stingless bee Scaptotrigona pectoralis (Dalla Torre). Stingless bees have an important role as pollinators of many wild and cultivated plant species in tropical regions. Little is known, however, about the interaction between floral fragrances and the foraging behavior of meliponine species. Thus we investigated the chemical composition of the extracts of citric (lemon and orange) flowers and their effects on the foraging behavior of the stingless bee Scaptotrigona pectoralis. We found that each type of flower has its own specific blend of major compounds: limonene (62.9%) for lemon flowers, and farnesol (26.5%), (E)-nerolidol (20.8%), and linalool (12.7%) for orange flowers. In the foraging experiments the S. pectoralis workers were able to use the flower extracts to orient to the food source, overlooking plates baited with hexane only. However, orange flower extracts were seemingly more attractive to these worker bees, maybe because of the particular blend present in it. Our results reveal that these fragrances are very attractive to S. pectoralis, so we can infer that within citric orchards they could be important visitors in the study area; however habitat destruction, overuse of pesticides and the competitive override by managed honeybees might have put at risk their populations and thus the ecological services they provide to us.

Euglossine bee communities in small forest fragments of the Atlantic Forest, Rio de Janeiro state, southeastern Brazil (Hymenoptera, Apidae)

Euglossine bee communities in small forest fragments of the Atlantic Forest, Rio de Janeiro state, southeastern Brazil (Hymenoptera, Apidae). Euglossine bees are important pollinators in forests and agricultural areas. Although the structure of their communities is critically affected by anthropogenic disturbances, little is known about these bees in small forest fragments. The objectives of this study were to analyze the composition, abundance, and diversity of euglossine bee species in nine small fragments of different phytophysiognomies of the Atlantic Forest in southeastern Brazil, and to identify the environmental variables that may be related to the species composition of these communities. Males were sampled quarterly from May 2007 to May 2009 with aromatic traps containing methyl cinnamate, vanillin, eucalyptol, benzyl acetate, and methyl salicylate. A total of 1558 males, belonging to 10 species and three genera of Euglossina were collected. The richness ranged from five to seven species per fragment. Euglossa cordata, E. securigera, Eulaema nigrita e E. cingulata were common to all fragments studied. The diversity differed significantly among areas, ranging from H' = 1.04 to H' = 1.65. The precipitation, phytophysiognomy, and altitude had the highest relative importance over the species composition variation. The results presented in this study demonstrate that small forest fragments are able to support populations of euglossine bee species, most of which are widely distributed and reportedly tolerant to open and/or disturbed areas and suggest that the conservation of such areas is important, particularly in areas that are regenerating and in regions with agricultural matrices where these bees can act as important pollinators

Orchid bee baits attracting bees of the genus Megalopta (Hymenoptera, Halictidae) in Bauru region, São Paulo, Brazil: abundance, seasonality, and the importance of odors for dim-light bees

Nocturnal bees in the genus Megalopta Smith, 1853 are generally collected using artificial light sources. However, between 1993 and 2000, a total of 946 females (no males were captured) were captured using aromatic baits commonly used for orchid bees (Euglossini) in five localities in Bauru region, São Paulo, Brazil. Aromatic compounds used in bait traps were: benzyl acetate, eucalyptol, eugenol, skatole, methyl salicylate, and vanillin. The Megalopta species collected were: M. guimaraesi (71.2% of total number of specimens), M. amoena (28.1%), and M. aegis (0.6%). Using the data from these traps, we showed that there was a positive and significant correlation between the abundance of individuals and meteorological factors, rainfall and temperature. Bees were more commonly collected in the spring (September to December) and summer (December to March) than in the autumn and winter, the latter characterized for being a drier and colder period. Variations in the abundance were also detected among localities and years. The most attractive compounds were eugenol (54%), methyl salicylate (22%), and eucalyptol (16%). The ability to detect smells may have an important role in searching for flowers during dim-light conditions. We suggest the use of aromatic compounds in future studies on the biology of Megalopta in the Neotropical region.

First host record for the cleptoparasitic bee Rhathymus friesei Ducke (Hymenoptera, Apidae)

The genus Rhathymus contains only obligatory cleptoparasitic species whose hosts belong to the genus Epicharis (Apidae, Centridini). Host information is available for only four of the 20 species of Rhathymus. In this note a new host record is added, in which the parasitism by R. friesei on nests of Epicharis (Epicharoides) picta is documented.

Notes on the systematics of the orchid-bee genus Eulaema (Hymenoptera, Apidae)

Notes on the systematics of the orchid-bee genus Eulaema (Hymenoptera, Apidae). The classification of the genus Eulaema is modified in order to make it congruent with recent phylogenetic hypotheses based on molecular data. The speciosa group, containing E. peruviana, E. speciosa and related species, is removed from E. (Eulaema) and transferred to E. (Apeulaema). New morphological characters are presented to support the revised scope of the subgenera and their diagnostic features are revised. Six species groups are recognized herein: two in E. (Apeulaema) and four in E. (Eulaema). A list of valid species in each species group and an identification key to males of each of the subgenera and species groups are provided. Finally, an older overlooked designation of a type species for Eulaema is presented in the Appendix.