What feature is common to cluster flies?

Cluster flies are characterized by their distinct appearance, which includes yellow or golden hair on the thorax. This feature is a key identification trait that helps differentiate them from other fly species, such as house flies, which do not have this coloration. The presence of the golden or yellowish hair contributes to their unique look and assists pest management professionals in correctly identifying and managing these pests.

While other options may contain elements that could apply to certain fly species, they do not accurately define the cluster fly. For example, cluster flies are typically inactive and tend to move indoors more during the fall and winter seasons to seek warmth, rather than being predominantly present indoors in summer, which is more characteristic of some other flies. Additionally, while cluster flies are larger than house flies, this is not as defining a characteristic as their coloration. Lastly, a gray striped thorax is not a recognizable trait of cluster flies, which further underscores the importance of their yellow or golden thoracic hair for identification.