The apple maggot uses Batesian mimicry as a method of defense, with coloration resembling that of the forelegs and pedipalps of a jumping spider (family Salticidae).

The apple maggot larvae are often difficult to detect in infested fruit due to their pale, cream color and small body size.

Adults emerge from late June through September, with their peak flight times occurring in August.

During the pupal stage, the larva is initially light yellow, but turns yellow-brown within hours and darkens.

[1] Adult female R. pomonella are shiny black with white markings and an average length of 6.25 mm.

Male R. pomonella have a similar appearance to the females but are smaller with an average length of 4–5 mm; the size of the abdomen is the main difference, with only five of the seven segments visible (the sixth and seventh are retracted under the fifth).

[2] California quarantine inspection records show apple maggot infest fruit have been intercepted at border patrol stations since around 1950.

A misidentified apple maggot, originally thought to be the snowberry maggot Rhagoletis zephyria, was found in the Oregon Department of Agriculture (ODA) tephritid fly collection, and the fly was collected in 1951 in Rowena, Oregon.

They are believed to have been spread through contaminated apples, most likely to have been accidentally introduced to the western United States multiple times over the past few decades.

[3][4] This theory is supported by lack of R. pomonella infestation on C. douglasii in Washington, Oregon, and Idaho, implying that the fly in these regions is not native on hawthorn.

[7] Flies emerge in the summer beginning in June and continuing through August and September, and eggs are laid in the apple fruit.

Larvae spend the pupal stage in the soil at a depth of one to two inches in the ground or sometimes in decayed fruit.

Male and female flies feed constantly from the surface of their food source, primarily apples.

Softened apples allow larvae to grow rapidly and break down pulp, even to the point of feeding at the core.

The male waits and uncoils his spring-like penis, quickly entering the opening of the ovipositor when the female extends it.

[11] The maggot stage has other predators including several braconid wasps: Utetes canaliculatus, Diachasmimorpha mellea, and Diachasma alloeum.

[11] Opius mellus (Biosteres rhagoletis) was bred from puparia of apple maggots in Maine in 1914 and was also found in blueberry barrens.

Based on research performed by Guy Bush, Jeffrey Feder, and others, this constitutes a possible example of an early step towards the emergence of a new species, a case of sympatric speciation.

[13][14] In addition, the hawthorn and apple host races of R. pomonella are able to produce viable offspring in a lab setting, but in nature, flies maintain their genetic integrity partly because of allochronic premating isolation from differently timed adult eclosion.

[14] The hatched maggots burrow tunnels within the apples and cause them to fall prematurely and create unsightly brown spots.

Apple maggots may be killed by placing infested fruit in cold storage of 32 degrees Fahrenheit for forty days.