What is a primary characteristic of stable flies?

Stable flies are characterized by their painful bites, which differentiates them from many other fly species. Unlike houseflies, which do not bite, stable flies feed on the blood of mammals, often causing significant irritation and distress to their hosts. This biting behavior can lead to decreased productivity in livestock due to the pain and discomfort they experience.

The other options present characteristics that are not applicable to stable flies. While some flies may infest decomposing organic matter or prefer wounds, stable flies are primarily external feeders that target living animals, rather than infesting wounds. They are also not particularly influenced by moisture conditions, like rain, as they can often be found in various environments, including dry areas. Thus, the defining trait of stable flies, their painful bite, is what sets them apart as a significant pest in both agricultural settings and other environments where they may be present.