Most bees rely on flowering plants and hence are diurnal foragers. From this ancestral state, dim-light foraging in bees requires significant adaptations to a new photic environment. We used DNA sequences to evaluate the phylogenetic history of the most diverse clade of Apoidea that is adapted to dim-light environments (Augochlorini: Megalopta, Megaloptidia and Megommation). The most speciose lineage, Megalopta, is distal to the remaining dim-light genera, and its closest diurnal relative (Xenochlora) is recovered as a lineage that has secondarily reverted to diurnal foraging. Tests for adaptive protein evolution indicate that long-wavelength opsin shows strong evidence of stabilizing selection, with no more than five codons (2%) under positive selection, depending on analytical procedure. In the branch leading to Megalopta, the amino acid of the single positively selected codon is conserved among ancestral Halictidae examined, and is homologous to codons known to influence molecular structure at the chromophorebinding pocket. Theoretically, such mutations can shift photopigment l max sensitivity and enable visual transduction in alternate photic environments. Results are discussed in light of the available evidence on photopigment structure, morphological specialization and biogeographic distributions over geological time.

International audienceEcological studies lasting more than 1 or 2 years are not particularly common anywhere and in any taxonomic group. Ecological studies in orchid bees (Hymenoptera: Apidae) are not an exception and have focused on short-term scale. Long-term studies have been mostly neglected up to date. Orchid-bee males were attracted to five different scent baits in the same site every other year during a seven-year span, from 1997 to 2004, in an urban forest remnant, totaling four full years of samplings in between. In total, we captured 2188 bees from 14 species. Species diversity, evenness, and richness remained remarkably stable among years. The stability index, sensu Wolda, for the composite community revealed to be one of the highest ever recorded for insect communities. Our results suggest that orchid-bee populations may remain remarkably stable over the years even in a small (≈200 ha) area immersed in a metropolitan (≈3,000,000 inhabitants) matrix and that these urban areas should not be neglected in conservation efforts, since they seem to maintain viable populations of these important pollinators over time

Megalopta (Smith 1853) is a nocturnal and/or crepuscular bee genus, with Neotropical distribution. The present work presents a taxonomic revision of Megalopta with emphasis on the Brazilian species through diagnosis and description of species and an identification key for most species that occur in South and Central America, with figures and distribution maps. Moreover eight new species are described: Megalopta guarani sp. n, M. mura sp. n, M. piraha sp. n, M. munduruku sp. n, M. yanomami sp. n, M. xavante sp. n, M. mapinguari sp. n. and Megalopta karitiana sp. n. Sex association for the male of M. chaperi (Vachal, 1904) is presented. Also we present taxonomical notes of valid species, with designation of lectotypes, new synonymies and checklist of valid species. Now, 32 valid species are recognized for the genus, with 19 in the Brazilian fauna. The present work enables correct identification of the species, which should facilitate further studies with Megalopta.

There are twenty-seven described species in the nocturnal bee-genus Megalopta Smith, 1853 (Hymenoptera: Halictidae); of these, 10 were recorded from Brazil but none in the Brazilian state of Minas Gerais. Here, five species of Megalopta are recorded for this state, two of them described as new. Four of these species belong in the subgenus Megalopta Smith s.str.: M. (M.) aegis (Vachal, 1904), M. (M.) amoena (Spinola, 1853), M. (M.) sodalis (Vachal, 1904) and M. (M.) guimaraesi sp.n., and one: M. atlantica sp.n., belongs to the subgenus Noctoraptor Engel, Brooks & Yanega, 1997, which is recorded for the first time for Brazil.A key for the identification of these five species is provided. Based on the examination of the types of species described by H. Friese and J. Vachal, M. ecuadoria Friese, 1926 and M. ochrias (Vachal, 1904) are proposed to be junior synonyms of M. amoena; and M. aethautis (Vachal, 1904) is proposed to be a junior synonym of M. fornix (Vachal, 1904). Lectotypes are designated for M. aeneicollis Friese; 1926 , M. armata Friese, 1926 M. boliviensis Friese, 1926; M. cuprea Friese, 1911; and M. sulciventris Friese, 1926. Evidence that Megalopta s.str. is rendered paraphyletic by the recognition of the subgenus Noctoraptor is presented and the potential use of aromatic baits for the inventory of local Megalopta faunas is discussed.

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