Western cherry fruit fly

Egg: The egg is yellowish and elongated with a stalk at one end. It is about 1/30 inch long (0.8 mm) and is deposited under the cherry skin.
Larva: The larva is a creamy white, legless maggot, which is tapered at the head and blunt at the rear. It passes through three instars and grows to about 5/16 inch (8 mm) long. Maggots found in cherries may be those of the cherry fruit fly or could also be larvae of the family Drosophilidae. The Drosophila fruit flies do not attack fruit unless the skin has been physically damaged, allowing an opening for deposition of eggs. (NOTE: this generalization has changed with the arrival of spotted wing drosophila, Drosophila suzukii , which CAN attack undamaged fruit before it is fully ripe.) This usually happens when cherries are cracked because of wind or rain damage or bird feeding or are decayed. Larvae of the cherry fruit fly, and other Rhagoletis species, can be distinguished from the Drosophila species by examining the posterior end of the larvae. The posterior end of the cherry fruit fly larva is rounded and the anal spiracles, which are not raised, each have three darker lines extending laterally from the mid-line. The posterior of Drosophila larva has two protuberances on which the anal spiracles are found.
Pupa: The pupa is yellowish brown to dark brown and looks like a large grain of wheat. It is about 3/16 inch (4 mm) long.
Adult: The adult has a black body with white bands on the abdomen. The wings are transparent with a distinctive dark banding pattern. It can easily be distinguished from other fruit flies by the wing pattern. The fly is about 1/5 inch (5 mm) long. The female is slightly larger than the male.
Life history. Cherry fruit fly completes only one generation a year. It overwinters as a pupa in the soil. The pupae are affected by soil temperature and do not all develop at the same rate. Adults begin to emerge in May, about 5 weeks before harvest, and are active until 3 or 4 weeks after harvest. Peak emergence often coincides with harvest.
Adults live 16 to 35 days, depending on temperatures. They feed on deposits on the leaves, such as honeydew and pollen. Adult females undergo a 7- to 10-day preoviposition period before they are sexually mature. After mating, they lay eggs under the skin of the fruit. Females frequently feed on juices exuding from the puncture made during egg laying.
Each female can lay from 50 to 200 eggs in a 3-week period. The optimum temperature for egg laying is between 75 and 85 F. The eggs hatch in 5 to 8 days, and the larvae burrow towards the pit of the fruit where they are unreachable by most pesticides. When fully developed, 10 to 21 days after hatching, they bore their way out of the cherries and drop to the ground. Within a few hours they burrow into the soil to pupate. The majority develop into adults the following season, though a few remain dormant for two years.
Damage. Adults do no damage to fruit. Maggots, which develop inside the cherries, make the fruit unmarketable. In unsprayed trees a high percentage of fruit is likely to be attacked. The adult cherry fruit fly does not fly long distances so some unsprayed trees may remain uninfested for many years.