The stable fly, Stomoxys calcitrans, is a cosmopolitan pest of animals and humans found throughout most terrestrial habits on earth. Genetic studies of this insect indicate that populations in the United States may be nearly panmictic. Although larval development sites for this insect are primarily restricted to livestock operations, hence the name stable fly, large numbers of flies often appear in residential and recreational areas far from these locations. Frequent inundations of ocean beaches and lakeshore areas, known for more than 70 years in the United States, by this biting fly have had negative economic impacts on local tourism. One study, using self-marking technology, documented movement of flies to a beach in Florida from an agricultural region 225 kilometers to the northwest. However, neither the biological cause of movement nor the relationship of that cause to the atmospheric motion systems that help transport stable flies long-distances have been clearly defined.
The stable fly presents an excellent target for aerobiological studies. Large, the approximate size of a house fly, and relatively easy to find and identify because of its prominent beak-like mouthparts, the primary food sources for adult flies are a variety of large mammals. Because the stable fly is a serious pest of humans and animals, causing both economic damage and disease transmission, its physiology and behavior have attracted substantial interest from scientists for many years.
There are two techniques that can be employed to assess stable fly age. The first uses the condition of a female fly's ovaries to estimate the number of blood-meals she has taken. From that data we can estimate the number of days during which she has been in the vicinity of appropriate food sources. The second uses the amount of pterin in the eye of either sex to estimate the number of days that have passed since adult fly emergence.
To test the utility of age-grading techniques for studying the aerial movement of a stable fly population, we made collections of a large number of stable flies various distances from isolated feedlots in southwestern Kansas during 1996. Flies were collected from mid-June through the end of June, using truck mounted mobile insect traps and stationary insect traps. Stable flies were collected as high as three meters in the air. A drone aircraft was unsuccessful at collecting stable flies at higher altitudes, although a few other arthropods were collected during these aerial runs. Using the age-grading techniques described above, we were able to statistically differentiate among the mean ages of the flies collected on the feedlot, adjacent to the feedlot, and three or more kilometers from known larval development sites or bloodmeals. In addition, we were able to determine phenological differences among flies that had dispersed and those that remained near the feedlots.