Minute to medium-sized flies, with wing length 0.9-6.5 mm. Postocellar setae when present divergent. Color ranging from black, gray, or green to entirely yellow; wing normally hyaline, but in a few tropical species of the Old and New Worlds distinctively pictured or infuscated. Female terminalia consisting of highly modified segments 7-9. Segment 7 visible externally as a conical nonretractable oviscape. The larvae are usually miners in leafs or other plant parts.