Wikipedia
The Anthomyiidae are a large and diverse family of Muscoidea flies. Most look rather like small houseflies, but are commonly drab grey. The genus Anthomyia, in contrast, is generally conspicuously patterned in black-and-white or black-and-silvery-grey. Most are difficult to identify, apart from a few groups such as the kelp flies that are conspicuous on beaches.
The name Anthomyiidae was derived from Greek anthos (flower) plus myia (a fly). Some species are commonly called "root-maggots", as the larvae are found in the stems and roots of various plants. As larvae, some also feed on decaying plant material. The well-known grey "seaweed flies" or "kelp flies" (Fucellia) are examples. Others are scavengers in such places as birds' nests; yet other species are leaf miners; the family also includes inquilines, commensals, and parasitic larvae.
Some species in the family are significant agricultural pests, particularly some from the genus Delia, which includes the onion fly ( D. antiqua), the wheat bulb fly ( D. coarctata), the turnip root fly ( D. floralis), the bean seed fly ( D. platura), and the cabbage root fly ( D. radicum).