Black and big flies are called hemp flies. Hemp flies reproduce by viviparous way. Most species of hemp flies produce maggots on carrion, feces or rotten substances. A few species produce maggots on the wounds of mammals, and some species produce maggots on other insects and become parasites of these insects. Its larvae may be used to treat maggots of people and animals and extract longevity proteins. Moreover, the large-scale production of larvae and pupae can be used as animal feed; Its eggs are larger than those of mammals, and it is easy to operate microscopically. Recently, it has been found that its broken sub-head can be used as a gene carrier, and the transgenic rate can reach over 90% through intracytoplasmic injection of sperm. Therefore, it is possible for the rapid propagation of hemp flies to develop into genetically engineered flies.

The biggest difference between them and other flies in appearance is that they have some plaid patterns on their bodies. The chest is gray with light black stripes, and the abdomen has light gray and dark gray plaid patterns. There are 5~6 bristles in the middle of the back, and the shorter the bristles are, the closer they are to each other. There are cilia in the central depression of the lateral plate of the chest, sometimes very few, even only 1~2; R 1 pulse hairy; There is no tassel hair on the ventral surface of the femoral joint of the midfoot; There are long tassel hairs in the tibiofibular joint of the hind foot; The third backboard of abdomen has no middle edge bristle, and the fifth web has no small window, and its base is normal and not particularly arched; The membranous process of the male stem is completely ossified, with small teeth on it, and there is no obvious boundary between the end and the base of the lateral male body. The ventral process of the base is a pair of small sharp teeth, and the end is well developed, and the lateral process is not obviously differentiated. The lateral inserter is slender and has micro-teeth at the end.