There exisls great interest in using fruit-feeding adult nymphalid butterflies to monitor changes in tropical forest ecosystems. We intensively sampled the butterfly fauna of mid-elevation tropical moisl forest in southem Costa Rica with fruit bait traps to address a series of practical issues eonceming the development of a robust, efficient sampling programo Variation in the number of captures and escapes of butterflies at the traps was better explained by the time of day than by the age of bait. Species' escape rates varied widely, suggesting that short term, less intensive surveys aimed at determining presence or absence of species may be biased. Individuals did not appear 10 become "traphappy" of a recognize the traps as food sources. Considering the tradeoff between numbers of traps and frequency of trap servicing, Ihe most efficient sampling regime appears to be baiting and sampling the traps once every other day
Keywords: butterfly trapping, Costa Rica, moniloring, nymphalidae, tropical conservation