Spatial distribution, seasonality and trap preference of stable fly, Stomoxys calcitrans L. (Diptera: Muscidae), adults on a 12-hectare zoological park

Although this study was originally designed to compare the efficacy of two different stable fly traps within 10 sites at a 12-ha zoological park, seasonal and spatial population distribution data were simultaneously collected. The two traps included an Alsynite fiberglass cylindrical trap (AFT) and a blue-black cloth target modified into a cylindrical trap (BCT). Both traps were covered with sticky sleeves to retain the attracted flies. Paired trap types were placed at sites that were 20-100 m apart. Distance between trap pairs within sites ranged from 1 to 2 m, and was limited by exhibit design and geography. Both trap types reflect/refract ultraviolet (UV) light which attracts adult S. calcitrans. During this 15-week study, AFTs captured significantly more stable flies than the BCTs at 8 of the 10 sites. Of the 12,557 stable flies found on the traps, 80% and 20% were captured by AFTs and BCTs, respectively. The most attractive trap site at the zoo was at the goat exhibit where most stable flies were consistently captured throughout the study. This exhibit was 100 m from the other exhibits, next to a small lake, and adjacent to a field containing pastured exotic ungulates, rhea and ostrich. Stable fly populations peaked in early June then slowly decreased as the last trapping date approached. We believe this to be the first seasonality data collected at a zoological park. Results demonstrate the use of urban zoos by stable flies and the need to develop environmentally friendly stable fly management systems for zoos.