An animal-baited trap was developed that collected an average 369 live flies per hour in an area where the population of field flies is estimated to be 13,200. However, it was cumbersome and difficult to move from on location to another. Therefore, a smaller portable trap that was baited with dead stable flies, Stomoxys calcitrans (L), was constructed. The smaller trap was easier to set up but collected fewer live flies and was subject to breakage if placed in pastures with cattle. In an area with an estimated fly population of 66,000, the collection rate of the smaller trap was 50 flies native stable flies for biological assays during sterile male releases on St. Croix, U.S. Virgin Islands.