Visitantes florais de plantas invasoras de áreas com fruteiras irrigadas

weeds can impair yield of irrigated fruit crops, studies about their ecology being needed, especially ways of reproduction and association with insects. this work was carried out in petrolina, pe, brazil with the objective of identifying the floral visitors of weeds, and classifying them as pollinators and pollen and/or nectar thieves, according to their behavior. the observations were made between may and october of 1998, in 26 not consecutive days, between 7:00 am and 4:00 pm. the weeds were classified in nectariferous and polliniferous when these were visited exclusively for collection of nectar or pollen, and mixed when these were visited to collect both. a grade system was adopted for the frequency evaluation: a- number of visits >30, b - between 10 to 30, c - <10. among the 24 weeds observed, 14 were classified as nectariferous, six as polliniferous and four were considered mixed. among the floral visitors, the following bees were registered (xylocopa grisescens, x. frontalis, centris aff. perforator, ptilotrix aff. plumata, diadasina riparia, apis mellifera, trigona spinipes, eulaema nigrita), butterflies (ascia monuste, papilio thoas brasiliensis, agraulis vanillae) and hummingbirds (phaethornis sp., chlorostilbon aureoventris). the bees were predominant in number of species (61.5%) as well as in the frequency of visits. they acted as pollinator agents in 83% of weeds visited. the butterflies were considered nectar thieves, and they acted as pollinator agents only in the case of the species of emilia. the hummingbirds acted as pollinators for all visited species.