We field-tested two sticky traps used to monitor populations ofStrobilomyiaspp. developing in the French Alps: a bright yellow horizontal trap and a bright yellow vertical trap with purple stripes. Fluorescent yellow traps captured significantly more flies than nonfluorescent yellow traps. Males ofStrobilomyia melaniaAckland were trapped significantly more often than females of otherStrobilomyiaspecies regardless of sex. Significantly more males were trapped per week when males were removed daily rather than weekly. Spectral patterns of the colors used in this experiment changed only slightly after 1 wk of exposure to sunlight and did not affect the daily captures of flies.