In urban landscapes, gardens provide refuges for bee diversity, but conservation potential may depend on local and landscape features. Foraging and population persistence of bee species, as well as overall pollinator community structure, may be supported by the abundance, richness, and spatial distribution of floral resources. Floral resources strongly differ in urban gardens. Using hand netting and pan traps to survey bees, we examined whether abundance, richness, and spatial distribution of floral resources, as well as ground cover and garden landscape surroundings influence bee abundance, species richness, and diversity on the central coast of California. Differences in floral abundance and spatial distribution, as well as urban cover in the landscape, predicted different bee community variables. Abundance of all bees and of honeybees (Apis mellifera) was lower in sites with more urban land cover surrounding the gardens. Honeybee abundance was higher in sites with patchy floral resources, whereas bee species richness and bee diversity was higher in sites with more clustered floral resources. Surprisingly, bee species richness and bee diversity was lower in sites with very high floral abundance, possibly due to interactions with honeybees. Other studies have documented the importance of floral abundance and landscape surroundings for bees in urban gardens, but this study is the first to document that the spatial arrangement of flowers strongly predicts bee abundance and richness. Based on these findings, it is likely that garden managers may promote bee conservation by managing for floral connectivity and abundance within these ubiquitous urban habitats.

The main cell types of the adult bee fat body are trophocytes and oenocytes; however, in pupae of some newly emerged bees, trophocytes are modified into cells called urocytes, which possibly function as a substitute for Malpighian tubules during metamorphosis when larval tubules are not functional and/or storage of urate salts is required. This study evaluated the morphology of urocytes in the stingless bee Melipona quadrifasciata and the possibility of maintaining these cells in primary culture. The urocytes M. quadrifasciata are white spherical cells with an irregular surface as observed by stereomicroscopy. They may be found individually or in groups associated with tracheae. Urocytes have a single, small, and spherical nucleus and cytoplasm rich in neutral polysaccharides, lipid droplets, protein, and granules containing calcium and urate salts. Our findings suggest that urocytes play a role in storage of neutral polysaccharides and calcium in M. quadrifasciata pupae and that these cells can be cultured for 72 h.

Chemical baits corresponding to natural orchid fragrance chemicals were used to attract and sample male orchid bees in terra firme and flood plain forest sites on the Tambo-pata Reserve in south-eastern Perú. The study was conducted monthly for two years. A total of 38 species of bees was collected at these chemical baits, and although most species were collected from both habitats, 11 species were significantly more common in one habitat than the other. There was considerable variation in the number and types of chemicals to which each of the orchid bee species was attracted.

Two cycles of seasonal abundance occurred annually in the number of orchid bee individuals and species collected at the chemical baits. A major peak occurred a month following onset of the wet season, and a minor peak occurred during the dry season. Species body size was related to seasonal activity, but additional factors such as flowering phenology and nest parasites were also probably involved.

The number of orchid bee species found on the Tambopata Reserve was similar to the number found in forest sites of eastern and central Brazil, Costa Rica, and Panamá. This homogeneity in species richness is in marked contrast to other insect groups such as Odonata, Lepi-doptera, Asilidae (Diptera), Tabanidae (Diptera), and Cicindelidae (Coleoptera), for which the species numbers recorded on the Tambopata Reserve are the highest for any similar sized area in the world.

The bumble and cuckooo bees (Hymenoptera: Apidae: Bombini; Bombus spp. and Psithyrus spp., respectively) are important plant pollinators and any decline in numbers or species constitutes a significant threat both to biological diversity and to whole economies. The distribution, status and factors threatening all 60 known taxa (species and subspecies) of Bombini of 11 countries of Western and Central Europe (Belgium, the Netherlands, Luxembourg, Denmark, Germany, Switzerland, Austria, Czech Republic, Slovakia, Hungary, Poland) were assessed from the beginning of the 20th century. The analysis was based on a literature review, unpublished data, personal communications, our own observations, and an expert review. The IUCN Red List categories were used for assessing the threat of extinction. Eighty per cent of taxa were threatened in at least one country of the region, and 30% of taxa were threatened throughout their range in the countries considered. More species went extinct per country in the second than in the first half of the 20th century, and four taxa went extinct in all 11 countries during 1951–2000. Amongst the factors adversely affecting the Bombini anthropogenic factors (particularly those associated with large-scale farming schemes) appear to be of greater importance than natural factors. To halt population declines and species extinctions it will be necessary to preserve aspects of traditional farming practices and for all Bombini to be afforded legal protection in all countries of the region. The implementation of the European Union's Common Agricultural Policy is likely to have the greatest single impact upon pollinators in the near future.

Primary flower resources to bees, i.e. those that satisfy basic needs, such as feeding and reproduction (Faegri & van der Pijl 1979), include pollen, nectar, oil, resin and gums. Resins are used in nest construction as a waterproof and structural material (Simpson & Neff 1981). It is also excellent antimicrobial compound, and a sticky defence against ant attacks (Armbruster 1984, Dressler 1982, Lokvam & Braddock 1999, Michener 1990, Roubik 1989, Sakagami et al. 1989). Plant species with flowers which produce terpenoid resins are rare (Armbruster & Webster 1979). Clusia L. (Clusiaceae), Clusiella Planch. & Triana (Clusiaceae), and Dalechampia L. (Euphorbiaceae) are the only known plants that secrete resins from floral structures (Armbruster 1984, Armbruster & Webster 1979, Bittrich & Amaral 1996). Although resin-producing plants provide an essential resource for a large number of bees in tropical communities, there are few studies about resin-collecting bees on Clusia spp. Skutch (1971) was the first to report visits on Clusia by stingless bees to collect floral resin. Other reports include observations on C. odorata Seem. (Croat 1978, Ramirez & Gomez 1978), C. alata Pl. & Tr. (Ramirez & Gomez 1978), and C. nemorosa G. F. W. Meyer (Armbruster 1984, Bittrich & Amaral 1996, Lopes & Machado 1998, Mesquita & Fransciscon 1995). Recently, Bittrich & Amaral (1996, 1997) have described the flower morphology and pollination biology of other Clusia species from Central America and Venezuela.