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Nearctic Sarcophagidae often perch on lichen-covered logs a tree trunks; on which they am chyptically colored. Costa Rican Sarcophagidae have the same basic color pattern, but rarely land on tree trunks. Nevertheless, Blaesoxipha plinthopyga (Wiedemann) takes stations on tree trunks in Costa Rican urban areas. It evidently immigrated from southwestern U.S. deserts, but only to Neotropical urban areas where lizard populations had been reduced. The metallic blues or greens of Neotropical sarcophagids am evolutionary effects of lizard predation. It is suggested that lizards forced sarcophagids from trunks, sometimes to green foliage where they were selected for metallic greens or blues as in Calliphoridae. The tropical abundance of vertebrate carrion feeders may also limit the distribution of B. plinthopyga.