How long do fruit flies live? The life cycle from egg to adult
Short answer: At 25 °C the fruit fly (Drosophila melanogaster) goes from egg to adult in about 8–10 days. Adults live from a few weeks to two months depending on temperature and food; heat shortens life (about a month at 29 °C). A female can lay around 400 eggs in her lifetime.
Four stages: egg, larva, pupa, adult
| Stage | Duration at 25 °C | What happens |
|---|---|---|
| Egg | 12–15 hours | The female lays it on fermenting fruit; the embryo develops. |
| Larva (3 stages) | about 4 days | The larva eats the fruit and its yeasts and moults twice. |
| Pupa | about 4 days | The last larval skin hardens into a brown case; inside, the body is rebuilt. |
| Adult | several weeks | The fly emerges, its wings unfold, and within hours it can mate. |
Egg. The female lays her eggs a few at a time on the surface of fermenting fruit or rotting plant matter. Two thin filaments at the front of the egg let it breathe even when it is half buried. At 25 °C the egg hatches within half a day.
Larva. The white, legless larva starts eating as soon as it hatches. It passes through three larval stages, shedding its skin between them, and gains weight many times over in about four days. In the last stage it leaves the food and wanders off to find a dry place to pupate.
Pupa. The larva's last skin hardens and darkens into the pupal case. Inside, metamorphosis begins: most larval tissues break down, and wings, legs, antennae and compound eyes grow from small groups of cells that were set aside in the larva (imaginal discs).
Adult. The fly pushes open a lid at the front of the case and climbs out. For the first hours its body is pale and its wings are crumpled; fluid pumped into the wings unfolds them, and the body darkens within a few hours. Females are ready to mate 8–12 hours after emerging. Egg laying starts soon after, reaching 50–70 eggs a day at its peak and around 400 over a lifetime.
Temperature changes everything
Fruit flies do not make their own body heat, so how fast they develop depends on the temperature around them. Approximate time from egg to adult:
- 28 °C: 7 days (fastest)
- 25 °C: 8.5 days
- 18 °C: 19 days
- 12 °C: more than 50 days
Hotter still, heat stress slows development again (about 11 days at 30 °C). Adult lifespan follows temperature too: around a month at 29 °C, and more than two months in cool laboratory conditions. That is why labs keep their fly stocks at 18 °C to slow them down and run experiments at 25 °C to speed them up.
Where do kitchen fruit flies come from?
Fruit flies are drawn less by fruit itself than by the yeasts growing on it. Alcohol, vinegar (acetic acid) and fruity esters rising from ripe, fermenting fruit attract them from a distance; one study found that yeast alone was enough to attract flies, make them lay eggs and feed their larvae. Flies can come in through a window, or eggs may already have arrived on the fruit.
Because the life cycle takes about ten days and one female lays hundreds of eggs, a single forgotten banana can fill a kitchen with flies within two weeks. To prevent it:
- Keep overripe fruit in the fridge or in a closed container.
- Clean the places where fermenting scraps collect: bins, compost and sink drains.
- A simple trap: a small dish of apple cider vinegar with a drop of washing-up liquid. The vinegar smell draws flies in; the soap lowers the surface tension, so a fly that lands sinks.
Sources
- Drosophila melanogaster (life cycle, development times, reproduction). Wikipedia. https://en.wikipedia.org/wiki/Drosophila_melanogaster
- Becher PG et al. (2012). Yeast, not fruit volatiles mediate Drosophila melanogaster attraction, oviposition and development. Functional Ecology 26(4): 822–828. https://lup.lub.lu.se/search/publication/2991550