Fruit flies come about in the same manner as any other fly does. Fruit flies will lay their already fertilized eggs in particularly mushy decaying food. These eggs hatch into maggots within 24 to 30 hours after being laid. Once they have hatched into maggots after about a week of being alive they will burrow deeper into the environment they hatched in and then emerge later as grown flies.
Very soon after they start the process all over again becoming sexually active only two days after they have matured into adult flies. Female fruit flies will lay hundreds of eggs in their short lifespan. A population of fruit flies can multiply very rapidly.
