In 1979 it was discovered in Oregon and has since moved into California, Washington, and other Western states. Hawthorn and apples are favored host plants, but cherries, pears, and other fruits have been attacked. Adult flies are somewhat smaller than houseflies and have clear wings with characteristic black bands, a pronounced white spot on the back of the thorax, and a black abdomen with light-colored crossbands.
Female flies have four crossbands on the abdomen, and males have three.
The apple maggot is closely related to the walnut husk fly and cherry fruit fly. However, it is difficult to distinguish apple maggot from snowberry maggot, a close look-alike that occurs throughout California, but which does not attack apples and pears. Larvae are cream-colored maggots with a blunt posterior and a tapered front end that contains two black mouth hooks. Browning of the trails occurs as the apple responds to this injury and bacteria associated with maggots cause fruits to rot internally. Because the apple maggot feeds within fruit, biological control agents have not been very effective.