Drosophila: Life Cycle

Scientists study Drosophila as a model specimen because of their very short life and reproduction cycle. In fact, their life cycles only last about 14 days! Since fruit flies don't live forever, reproduction is critical to keep the species alive.

Are you familiar with a butterfly's life cycle? If so, you'll see that Drosophila's life cycle is very similar to a butterfly's. They both undergo complete metamorphosis, which means that the young form looks very different from the adult! Unlike baby humans, who have all of their adult structures (arms, legs, fingers, nose, etc.) and look like small versions of adults, the baby fruit fly looks very different from the adult. The baby, or larva, looks like a small worm, and does not have adult structures like wings or legs.

Like many species, female fruit flies produce eggs and males produce sperm. When the egg and sperm unite, a new individual develops. In fruit flies, sperm is deposited from the male fruit fly into the female fruit fly. The female stores sperm inside of her. The eggs are fertilized when they pass through the oviduct on their way to being deposited on a food source.

Fruit flies begin their lives as an embryo in an egg. This stage lasts for about one day. During this time, the embryo develops into a larva. The first instar larva hatches out of the egg, crawls into a food source, and eats. The larva in each stage eats as much as possible! After a day, the first instar larva molts and becomes the second instar larva. Again, the larva in this stage eats and eats! After two days in this stage, the larva molts again to become the third instar larva. After three days of eating in this stage, the larva crawls out of the food source and molts again.

Following this molt, the larva stops moving and forms a pupa. Drosophila stays in the pupa for about five days. During this time, the metamorphosis, or change, from larva to adult is occurring. Adult structures, like wings, legs, and eyes develop.

When the adults emerge from the pupa, they are fully formed. They become fertile after about ten hours, copulate, the females lay eggs, and the cycle begins again. The whole life cycle takes about 12-14 days.

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