They place the eggs just under the skin through a puncture made by the sharp, needlelike ovipositor. Females may lay eggs over an extended period of time. Eggs usually hatch in less than a week. Maggots hatching from these eggs tunnel through the apple, causing a breakdown and discoloration of the pulp. The mature maggots leave the fruit and enter the soil, where they transform to the pupal stage.
Most pupae remain in the soil until the following summer.
They emerge at the normal time during the second summer. These are not of much significance to growers who maintain good control every year, but they might be of importance in an orchard where the pest was allowed to become very numerous. Even after a vigorous and successful control program had been carried out for one year, there would still be some carryover for the second year. The apple maggot causes two forms of injury. The flesh surrounding a puncture where eggs are deposited in immature fruit often fails to grow with the rest of the apple and becomes a sunken, dimplelike spot in the surface.