Stable Fly, Stomoxys calcitrans (L.), Dispersal and Governing Factors.

Although the movement of stable fly, Stomoxys calcitrans (L.), has been studied, its extent and significance has been uncertain. On a local scale (<13 km), fly movement occurs between host animals and resting sites to feed and mate, mainly at on-farm locations where herbivorous livestock regularly congregate. Small numbers emigrate from livestock congregation sites in search of other hosts and oviposition substrate, mostly within <1.6 km. Such local movement occurs by flight ~90 cm above ground, or with moving livestock. While stable flies are active year-round in warm latitudes, cold winters in temperate areas result in substantial population and activity declines, limiting movement of any sort to warmer seasons. Long-distance dispersal (>13 km) is mainly wind-driven by weather fronts that carry stable flies from inland farm areas for up to 225 km to beaches of northwestern Florida and Lake Superior. Stable flies can reproduce for a short time each year in washed-up sea grass, but the beaches are not conducive to establishment. Such movement is passive and does not appear to be advantageous to stable fly's survival. On a regional scale, stable flies exhibit little genetic differentiation, and on the global scale, while there might be more than one "lineage", the species is nevertheless considered to be panmictic. Population expansion across much of the globe likely occurred from the late Pleistocene to the early Holocene in association with the spread of domesticated nomad livestock and particularly with more sedentary, penned livestock.