Neotropical Entomology 32 (2) : 247-259 (2003) Plants Visited by Centris spp. (Hymenoptera: Apidae) in the Caatinga to Obtain Floral Resources ABSTRACT -A revision of flower visitation records by bees of the genus Centris in the Caatinga, the xerophylous vegetation predominant in the semi-arid Northeastern Brazil, is presented. This revision includes, besides literature data, results from six annual surveys of the bee fauna and visited flowers, undertaken in limited areas of the States of

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... a, Bahia and Rio Grande do Norte, Brazil. A total of 21 species of Centris were registered in these surveys, the highest species richness was observed in Castro Alves and Itatim (Bahia), 12 and 10 species, respectively. The higher species richness probably results from the presence of elements in adjacent biomas, since these two places are close to the eastern limit of the Caatinga. A total of 69 species of visited plants were registered. Caesalpinia pyramidalis (Caesalpiniaceae) and Melochia tomentosa (Sterculiaceae) are important nectar sources, as indicated by the higher number of Centris visitors' and by the number of areas where they occurred. Species of Chamaecrista, Senna (Caesalpiniaceae), and Solanum (Solanaceae) seem to be important pollen sources. Chamaecrista nictitans and C. pascuorum are registered for the first time as pollen sources for Centris hyptidis. The oil sources registered in the Caatinga for Centris bees belong to the families Malpighiaceae and Scrophulariaceae. Among the more abundant species of Centris, those not restricted to the Caatinga region (C. fuscata, C. aenea, C. tarsata and C. trigonoides) present a high similarity in the spectrum of visited plants. C. hyptidis, an endemic species, has a somewhat distinct niche.