Effectiveness of two sampling protocols to survey orchid bees (Hymenoptera: Apidae) in the Neotropics

We compared the performances of two different methodologies for collecting orchid bees (Hymenoptera: Apidae): active sampling (at chemical baits with hand nets) versus passive sampling (with baited traps). Data were retrieved from previous field studies in which both methodologies were employed simultaneously. We evaluated the effectiveness of each method in terms of the number of species collected and the composition of the bee species through paired t test and Permutational Multivariate Analysis of Variance, respectively. Active sampling collected significantly more bee species than passive sampling in all but one study. The composition of bee species collected by each of the two methods was also significantly different. Larger bees belonging to Eulaema and Eufriesea species tended to be more frequent in traps. In contrast, all Euglossa species presented comparatively higher relative frequencies with active sampling. We challenge previous assertions that both methodologies are equally effective and argue that insisting on the sole use of baited traps in orchid-bee inventories may result in retrieving strongly biased raw data which will eventually lead to incorrect conclusions about the actual composition of orchid-bee assemblages. Since orchid bees have been more and more used as key organisms in studies on environmental impact in the Neotropics, particularly in Brazil, and the passive sampling methodology has been adopted as the "official" one by the Brazilian environmental agency (IBAMA), we suggest a re-evaluation of this practice and the adoption of the more expensive, but more reliable, methodology of using well-trained field researchers to actively collect data on these important Neotropical pollinators.