Flies in the genus Pollenia are commonly called "cluster" flies after their habit of  gathering in conglomerations. They superficially resemble house flies, but are slightly larger. Cluster flies at rest overlap their wings, whereas house flies do not. The thorax is without distinct stripes, and is covered with short, yellow-gold hairs. The abdomen is dark grey, with patches of darker gray, resembling the coloring of some flesh flies in the family Sarcophagidae. It is said these flies, when crushed, exude an aroma of "buckwheat honey." [1]  I don't know about you, but I  can think of better things to do with my time than sniff crushed flies.