How Long Do Fruit Flies Live? Fruit Fly Lifespan Calculator

How long do fruit flies live?

Fruit flies live longer than most people expect. In a normal home, extension entomologists at the University of Kentucky say adult fruit flies typically live around one month. In a laboratory, where flies get fresh food every couple of days and nothing eats them, the common fruit fly lifespan is longer still: about 38–63 days on average at 25 °C (77 °F), and roughly two to four months in a cool room.

So how long can a fruit fly live at most? The longest averages in the studies we use are about 150 days, recorded for lab flies kept at 11 °C (52 °F) (Massie et al. 1985). That is close to the cold limit: below about 11 °C, cold starts to harm fruit flies in other ways, and they stop developing altogether.

Three things decide how long do fruit flies live for — or, as people often type it, "fruit flies live how long":

• Temperature — by far the biggest factor. Warm flies live fast and die young; cool flies live slowly and much longer.
• Sex and mating — the gap between males and females is small and changes with temperature, but mating shortens a female's life.
• Food and surroundings — lab flies have perfect food and no predators, spiders or fly swatters, which is why their lifespan is longer than in a kitchen.

Lab vs a typical home

Whichever way the question is phrased — "how long is a fruit flies' lifespan", "how long is the life of a fruit fly" or the fruit flies' life span in a kitchen — the honest answer is a range, because the setting changes it so much. The lab figures are the ceiling; a home is usually well below it.

In short, how long fruit flies live comes down to the room they are in. Add the egg, larva and pupa stages and a whole fruit fly life is only about 9–19 days longer than the adult part, depending on temperature (Bloomington Drosophila Stock Center). The calculator above combines these into one answer for your room. One thing it can't account for is food running out: if you've cleared the fruit bowl, adults survive only a few days without food (see our die-off timeline).

Fruit fly lifespan in days: what the research shows

Here is the fruit fly lifespan in days, as average adult lifespans measured in lab studies of Drosophila melanogaster. Mołoń and colleagues (2020) tested four wild-type fly lines from Australia, Canada, Benin and the standard Oregon R lab strain at 20, 25 and 28 °C, with males and females kept apart; Massie and colleagues (1985) measured Oregon R flies at 11, 20, 25 and 30 °C. Rows marked "calculated" sit between measured temperatures.

The Drosophila lifespan ranges are wide because fly lines differ. At 20 °C, for example, Australian flies averaged about 120 days, while Oregon R lab flies averaged about 90–106. At 25 °C — a typical lab temperature — the drosophila melanogaster lifespan averaged 38–62 days for males and 52–63 days for females. A standard lab handbook gives 45–60 days at 25 °C "under optimal conditions" and notes that lifespan is "considerably shorter under normal culture conditions" (Ashburner et al. 2005, via BioNumbers).

The average lifespan of a fruit fly — or the average lifespan of fruit fly populations in general — also depends on what you count. Most published fruit flies lifespan figures, including all of these, are for the adult stage only. These figures are averages for adults, starting from the day they climb out of the pupal case. Some flies die in the first week and a few live much longer than average: in the 2020 study, the longest-lived single flies at 20 °C reached 124–164 days.

How long do fruit flies live indoors and in your house?

How long do fruit flies live in your house? Around a month is the figure from the University of Kentucky, and that matches what the lab numbers predict once you allow for real life. In a kitchen at about 21 °C (70 °F), lab flies would average 72–116 days, but house flies of every kind face hazards lab flies never meet:

• food that dries out, gets thrown away or goes in the fridge;
• spiders, traps, cleaning and the occasional clap of the hands;
• cold windowsills at night and hot spots near ovens or sunny windows;
• mating, which shortens the lives of females in particular.

That's why the answer to how long do fruit flies live indoors is usually "weeks, not months". Fruit flies are most common indoors in late summer and autumn, when ripe produce comes in from the garden and the shop, and adults can also fly in through screens that are not fine enough (University of Kentucky).

Why it can feel like they live forever

If you have had fruit flies for six weeks, you are almost certainly not looking at the same flies. New adults keep emerging from wherever they are breeding — a forgotten potato, the recycling bin or the slime in a drain — and they replace the ones that die. The calculator's "days since you noticed them" option shows how far through a typical adult life that is. For how quickly new ones appear, see the fruit fly life cycle calculator.

Male vs female fruit fly lifespan

Do female fruit flies live longer? In most lab studies, slightly — but not always. In the 2020 study, females out-lived males in most fly lines at 25 °C: averages were 52–63 days for females against 38–62 days for males. At 20 °C the sexes were very close, and at 28 °C the Oregon R females actually died sooner than the males.

The bigger difference is mating. The flies in those lifespan studies were virgins. The same paper notes earlier work showing that virgin females live about twice as long as mated females, and that sexual activity also shortens male lives (Mołoń et al. 2020, citing earlier studies). In your kitchen, almost every female has mated, so the male vs female fruit fly lifespan gap you would see is smaller than the lab averages suggest.

The calculator's "Males" and "Females" options show the lab range for each sex; "Mixed" spans both, which is the right choice for flies in a home.

Why temperature changes fruit fly life expectancy

Here is how temperature affects fruit fly lifespan. Fruit flies are cold-blooded. Their body temperature follows the room, and so does the speed of everything inside them — breathing, burning fuel and wearing out. A classic 1976 study of male flies at 18, 21, 27 and 30 °C found that life span is temperature dependent and that flies "are living faster" at the higher temperature, using more oxygen and losing vitality sooner (Miquel et al. 1976). This is called the rate-of-living idea.

The numbers show how strong the effect is. From the measured points, fruit flies life expectancy drops from about 152 days at 11 °C to about 81 at 20 °C, 62 at 25 °C and 25 at 30 °C (Massie et al. 1985). Each extra degree in a warm room takes days off a fly's life. The 2020 study confirmed that 28 °C shortened life in all four fly lines and both sexes, and linked shorter lives to a higher metabolic rate measured as heat output.

Fruit fly lifespan at room temperature, in summer and in winter

• Fruit fly lifespan at room temperature (about 21 °C / 70 °F): 72–116 days in the lab; around a month in a home.
• A warm summer kitchen (26–28 °C / 79–82 °F): 26–60 days in the lab — shorter lives, but faster breeding, which is why summer infestations explode.
• A cool winter room (18 °C / 64 °F): 97–134 days in the lab. Below about 11 °C, fruit flies can't develop at all (Da Lage et al. 1989), which is why they are rarely a winter problem outdoors.

So the fruit fly lifespan in summer vs winter is a trade-off: summer flies live less than half as long, but they reproduce much faster.

Do fruit flies die in winter? →

Fruit fly longevity and ageing research

Few animals have taught scientists more about ageing than the fruit fly. So why are fruit flies used in ageing research? Researchers have used Drosophila to study ageing since Loeb and Northrop's work in 1916 (Mołoń et al. 2020). The reasons why fruit flies are used in ageing research are practical:

• A short life. A whole lifespan experiment takes weeks or a few months, not decades.
• A fully sequenced genome and powerful genetic tools, so scientists can switch single genes on or off and watch the effect on lifespan.
• Cheap, simple care: thousands of flies live on yeast, sugar and agar in small vials.

That is why fruit fly longevity research has covered so many factors: genes linked to oxidative stress, DNA repair and insulin-like signalling; diet; mating; and temperature. Two diet findings stand out. Eating less — dietary restriction — can lengthen a fly's life, while a fat-rich diet can shorten it (summarised by Mołoń et al. 2020). This is the main way food availability affects fruit fly lifetime in the lab: not just whether there is food, but how rich it is.

Fruit fly lifespan compared to humans

A fruit fly's month in your kitchen is a whole life: egg, larva, pupa and adult. Global human life expectancy is about 73 years (WHO), almost 900 times longer than a month. Ageing in flies shows up as rising death rates and falling reproduction and physical performance — the same definition of ageing researchers use for other animals (Mołoń et al. 2020) — so a short-lived fly lets scientists test ideas about ageing quickly.

Fruit fly lifespan compared with other small flies

Small flies in the house are easy to mix up, and their lives differ a lot. A fruit fly vs house fly lifespan comparison is close — both live weeks — but set fruit flies beside gnats and the gap is wide: fungus gnats and drain flies live only days as adults. Mosquitoes sit in between; see how long mosquitoes live and how long house flies live for those insects.

The fruit fly is tan with bright red eyes and about 1/8 inch (3 mm) long, and it hangs around ripe fruit and bins (University of Kentucky). If your flies are dark and gather around houseplants or drains, they are probably gnats or drain flies — the gnat lifespan calculator covers those, and the fruit fly vs gnat identifier tells you which you have.

How this fruit fly lifespan calculator works

The calculator uses only measured averages. It starts from the lab points in the table above — 11, 20, 25, 28 and 30 °C — and for any temperature in between it draws a straight line between the two nearest points (linear interpolation). For each temperature it shows the range across the fly lines studied, so you see the spread rather than one falsely precise number.

• Males / Females use each sex's own figures. Mixed spans the lowest and highest of both.
• Comparison bars show the same fly 5 °C cooler and 5 °C warmer, within the sourced 11–30 °C range.
• Days since noticed is compared with the middle of the range for your temperature.
• Below 11 °C or above 30 °C, it asks for a temperature inside the studied range rather than guessing.

At 11 °C and 30 °C only one study gave a figure, and it did not report the sexes separately, so the same value is used for both. All flies in these studies were unmated and well fed, so treat the results as the upper end of what flies in a home achieve.

Frequently asked questions

These calculators give estimates for education. Real flies vary with strain, food, humidity and temperature. For a stubborn infestation, your local cooperative extension service can help identify the insect. We give no pesticide advice.