How long do flies live? House fly lifespan, life cycle and temperature

A house fly’s life is set largely by the temperature around it: in one laboratory study, half of the adult females had died after about 10 days at 35 °C, but not until about 44 days at 20 °C.

An adult house fly (Musca domestica) typically lives from about 10 days to two months, after spending roughly 1 to 2 weeks as an egg, maggot and pupa. Temperature is the biggest reason for the spread. Warm flies grow up fast and die young; cool flies take longer at every stage and live longer.

The lab numbers make the point. At a constant 20 °C, female house flies lasted a median of about 43.5 days, and at 35 °C about 10.1 days, a difference of more than four times. Without food, the LSU AgCenter puts adult survival at only two to three days.

Explain it like I’m busy:

• Egg to adult: as little as about 7 days in summer heat, about 14 days at room temperature.
• Adult house fly: a median of about 10 to 44 days in the lab, shorter when it is hotter.
• The “flies live one day” idea fits mayflies, which are not true flies at all.

Key facts about house fly lifespan

• Four stages: egg, larva (maggot), pupa and adult. A house fly egg hatches after 8 to 20 hours in ideal conditions, and the pupal stage takes 2 to 6 days depending on temperature (LSU AgCenter).
• Fastest development: egg to adult in as little as 7 days in summer conditions (UC IPM). A 2025 Texas A&M study recorded the first adults at 7.2 days at 37 °C and 13.9 days at 24 °C.
• Adult life: 25 days to two months depending on nutrition, and two to three days without food (LSU AgCenter).
• Temperature effect, measured: the median adult female life was about 43.5, 24.4, 16.7 and 10.1 days at 20, 25, 30 and 35 °C (Fletcher, Axtell and Stinner, 1990; days calculated by SciQuest from their published rates).
• Eggs: about 500 in a lifetime, in batches of 75 to 150 (LSU AgCenter). In the 1990 study, the total ranged from 184 eggs per female at 20 °C to 729 at 25 °C.

The house fly life cycle, stage by stage

The figure below shows the whole life on one clock. The top panel follows eggs from a Texas house fly population reared on lean pork at two constant temperatures. The bottom panel shows how long adults lasted at four temperatures in a North Carolina State University study.

1. Egg (hours): the egg hatches in 8 to 20 hours in ideal conditions (LSU AgCenter). In the Texas study the first larvae appeared at about 19 hours at 24 °C and about 9 hours at 37 °C.
2. Larva, or maggot (days): it molts through three growth stages, called instars. From the Texas timings, the larval stage took about 6.6 days at 24 °C and about 3.1 days at 37 °C (our subtraction of their published hours).
3. Pupa (days): the full-grown maggot stops feeding and becomes a pupa, inside which the adult body forms. LSU gives 2 to 6 days depending on temperature; the Texas timings work out to about 3.7 days at 37 °C and 6.6 days at 24 °C.
4. Adult (weeks): the stage most people mean when they ask how long a fly lives. Its length depends on warmth, food and sex, as the next section shows.

What a fly’s lifespan means: a body run by the thermostat

A fly can’t hold its own body temperature the way you do. Its chemistry runs at the speed the room sets. The useful picture is a clock whose speed is set by the thermostat: turn the heat up and every stage ticks by faster, including ageing.

Put in human terms, a fly kept at 35 °C runs through its adult life in about a week and a half. The same fly at 20 °C has about six weeks. Scientists have described this as flies “living faster” when warm: a 1976 study of about 3,500 male fruit flies found higher oxygen use and quicker loss of vigour at 21 °C than at 18 °C.

The thermostat picture has limits. It breaks down at the extremes, where heat stops speeding a fly up and starts damaging it. Green bottle blow fly larvae failed to complete development at 35 °C and 37 °C in one study, and at 8 °C and 10 °C.

How scientists measure how long flies live

The cleanest method is simple and slow. Researchers hold a group of newly emerged adults in a cage at a fixed temperature, give them food and water, and count the dead each day. The time at which half the flies have died is the median lifespan.

That is what M. G. Fletcher, R. C. Axtell and R. E. Stinner did at North Carolina State University, at 20, 25, 30 and 35 °C. They reported their results as a median mortality rate, the reciprocal of the days to 50% mortality. We turned those rates back into days.

Worked calculation: rate to days

Days to 50% mortality = 1 ÷ median mortality rate. For females at 20 °C, 1 ÷ 0.023 per day = 43.5 days. At 35 °C, 1 ÷ 0.099 per day = 10.1 days. The ratio 43.5 ÷ 10.1 = 4.3, so cool females lasted a little over four times as long.

Source: Fletcher, Axtell and Stinner (1990), Journal of Medical Entomology 27(5): 922–926, abstract. Days are SciQuest calculations (1 ÷ published median mortality rate), rounded to 0.1 day. Egg totals are as published. Constant laboratory temperatures.

Females outlived males at the three cooler temperatures, but not at 35 °C. A cooler fly also isn’t a more productive one: females at 20 °C laid only 184 eggs, about a quarter of the 729 laid at 25 °C.

A separate study by K. J. Farmer and R. S. Sohal points the same way. Male house flies kept at 28 °C had an average life span about 52% shorter than flies kept at 20 °C. The authors proposed that extra oxidative stress, damage from reactive forms of oxygen, is part of the reason. That explanation is a proposal, not settled.

What changes the answer

Temperature matters most, as the table shows. Food comes next: LSU AgCenter gives 25 days to two months for adults depending on nutrition, but only two to three days without food.

Lab versus wild is the biggest gap in the evidence. Every adult lifespan number on this page comes from flies that were fed and protected. We found no field estimate of wild house fly lifespan that we could verify, so treat these figures as what a fly can manage, not what a typical fly outdoors achieves.

Population and food source also shift development. The first Texas adults appeared at 13.9 days at 24 °C. An earlier dataset by Wang and colleagues (2018), as reported in the Texas paper, gives 297.4 hours, about 12.4 days, at 25 °C. In Punjab, Pakistan, house flies from warmer, lower-altitude areas developed faster and lived longer than flies from cooler, higher ones.

That is why published “house fly lifespan” figures disagree. The popular range of two to four weeks matches the 25 to 30 °C rows of the table. LSU’s upper figure of two months fits a cooler, well-fed fly. Neither is wrong, and neither applies everywhere.

How long other flies live: a comparison

Sources: as listed in each row; full references below. Blow fly days are SciQuest conversions of 288, 401 and 778 hours. Lab values at constant temperatures unless stated. Horse fly figures are for the whole family and vary by species.

The fruit fly is the odd one out. In these lab studies, a well-fed Drosophila at 25 °C outlived the median house fly at the same temperature, despite being far smaller. Nancy Linford and colleagues, in a standard lifespan protocol, write that adult males “typically live markedly shorter as temperature is increased.”

Horse flies flip the pattern. Their larvae live in wet soil or water, and the NC State guide says they may take a month to a year or more to develop. Purdue’s guide adds that very large species need two to three years. For many species, most of the life cycle happens out of sight, as a larva.

Why it matters to you

The timeline explains why flies seem to appear from nowhere in summer. If a bin, compost heap or pet waste sits for about a week in hot weather, that is long enough for eggs laid on it to become flying adults (our inference from the 7-day minimum).

The health side is real but should not be overstated. LSU AgCenter describes house flies as mechanical carriers of disease agents, meaning they carry microbes from one place to another, and lists E. coli, typhoid and cholera among them. UC IPM notes that they pick these agents up while feeding on animal feces. LSU notes this is a bigger problem where sanitation infrastructure is poor. House flies do not bite.

“But wait…” don’t flies live for only 24 hours?

That belief fits mayflies, not house flies. Adult mayflies live a few days, sometimes only hours, and have only leftover mouthparts, so they cannot eat or drink (Missouri Department of Conservation). Mayflies belong to the insect order Ephemeroptera. True flies, including house flies, fruit flies, blow flies and horse flies, belong to a different order, Diptera.

Even the mayfly isn’t short-lived overall. Its nymphs spend months or years in water before the brief adult stage.

Related questions

Do flies live longer in winter? In the lab, cooler flies live longer: about 43.5 days at 20 °C against 10.1 days at 35 °C for females. Outdoors, cold also slows or stops development, and we have not verified how house flies survive winter, so we leave that out.

How fast do fruit flies breed? At 25 °C, adults start to emerge about 9 days after eggs are laid (Linford and colleagues). That speed is one reason they are a favourite lab animal; their nervous system is now mapped in detail, as in our story on fly connectome simulations of walking.

Are all insects that look like flies actually flies? No. Mayflies, dragonflies and many others are in separate orders. Hoverflies are true flies, and their decline is part of a century of pollinator range losses in Europe.

Would ecosystems miss flies? The same question is often asked about their biting relatives; we looked at it in what would happen if mosquitoes went extinct.

In one sentence

A house fly spends about one to two weeks growing up and then usually a few weeks as an adult, and the warmer it is, the faster the whole clock runs.

Read next

• Three-neuron circuit may set the fly’s walking rhythm
• Most tracked bee species in Europe lost range over a century
• What would happen if mosquitoes went extinct

Sources

1. Fletcher MG, Axtell RC, Stinner RE (1990). Longevity and fecundity of Musca domestica (Diptera: Muscidae) as a function of temperature. Journal of Medical Entomology 27(5): 922–926. doi:10.1093/jmedent/27.5.922 (abstract read on PubMed).
2. Flint CA, Rhinesmith-Carranza J, Bell R, Tomberlin JK (2025). Development of the house fly, Musca domestica L., on pork tissue at two temperatures. Journal of Forensic Sciences 70(2): 619–626. Full text, PMC11874249.
3. McComic S, Carlton CE. Musca domestica, house fly (Diptera: Muscidae). LSU AgCenter (2022).
4. Gerry AC. Pest Notes: Flies. University of California Statewide IPM Program, updated May 2015.
5. Farmer KJ, Sohal RS (1987). Effects of ambient temperature on free radical generation, antioxidant defenses and life span in the adult housefly, Musca domestica. Experimental Gerontology 22(1): 59–65. PubMed abstract.
6. Khan HAA et al. (2019). Geographical variations in life histories of house flies, Musca domestica, in Punjab, Pakistan. Journal of Medical Entomology 56(5): 1225–1230. PubMed abstract.
7. Linford NJ, Bilgir C, Ro J, Pletcher SD (2013). Measurement of lifespan in Drosophila melanogaster. Journal of Visualized Experiments (71): 50068. Full text, PMC3582515.
8. Miquel J, Lundgren PR, Bensch KG, Atlan H (1976). Effects of temperature on the life span, vitality and fine structure of Drosophila melanogaster. Mechanisms of Ageing and Development 5(5): 347–370. PubMed abstract.
9. Pruna W, Guarderas P, Donoso DA, Barragán Á (2019). Life cycle of Lucilia sericata (Meigen 1826) collected from Andean mountains. Neotropical Biodiversity. doi:10.1080/23766808.2019.1578056 (abstract).
10. Kim H-C et al. (2007). Development of the greenbottle blowfly, Lucilia sericata, under different temperatures. Korean Journal of Applied Entomology 46(1). doi:10.5656/ksae.2007.46.1.141 (abstract).
11. Hill CA, MacDonald JF (2019). Horse and deer flies: biology and public health risk (E-246-W). Purdue Extension.
12. Waldvogel M, Apperson C. Horse flies and deer flies. NC State Extension (2001, revised 2022).
13. Townsend L. Horse flies and deer flies (ENTFACT-511). University of Kentucky Entomology.
14. Missouri Department of Conservation. Mayflies, field guide.

Disclosure: This article was drafted with AI assistance and checked against the sources above. The stage lengths, the days-to-50%-mortality values and the hour-to-day conversions are SciQuest calculations from the published figures; the graphic is a SciQuest original drawn from those numbers. Several sources were read as abstracts only, as marked. Spotted an error? See our corrections policy.