How Long Do Flies Live?

Houseflies are considered disgusting and can be the bane of some people’s existence. It’s not surprising, given their lifestyle. For instance, these dirty creatures eat and lay their eggs on filthy things like garbage, fecal matter, and even dead and decaying organisms. They then have no qualms landing on our pets, our food, and even us. It’s enough to put you off your meal.

If your yard never seems to lack a constant supply of flies – year round – you might be tempted to think these creatures are immortal. If not, they should at least be the ones we say have nine lives. It can seem like they never die.

Of course, like all animals, they do die. But how long do flies live? Here, we’ll cover flies, their life cycles, and their life spans. This information should help you understand why flies seem to be ever present. Hopefully, this knowledge will help you manage them as well.

The Life Cycle of a Fly

Flies undergo complete metamorphosis. This means that their life cycles contain four distinct stages: egg, larva, pupa, and adult. 

The cycle begins when a female fly lays eggs. A lot of eggs. A single female fly lays 100 to 150 eggs per batch, on average. Over a few days, that one fly can lay several batches of eggs for a total of around 500 eggs. Smaller flies lay fewer eggs.

Females deposit their eggs in warm, damp environments, which often are pretty gross. Places like compost piles, manure, or garbage are excellent options for her. If her eggs dry out, they will not hatch.

Fly eggs are usually white and roughly 1.2 millimeters long.

The eggs hatch into cream-colored larvae (also called maggots) about 12 to 24 hours after being laid. In warm weather, they can hatch within 8 hours. At this stage, they are about 3 to 9 millimeters long.

Larvae require high temperatures for proper development. The best temperature is between 95 and 100 degrees Fahrenheit. If this temperature is steadily maintained, larvae can grow and develop through three intermediate stages (instars) to the final larval stage in just 4 to 13 days.

As they grow, larvae eat the organic matter in their environment, be it feces or decaying plant or animal matter. Once they have reached the final larval stage, they move to a cooler, dryer area to metamorphose into pupae.

The fly undergoes many changes during the pupal stage, in which it is encased in a hard covering. Pupae are about 8 mm long and round at both ends.

As it develops, the pupa changes in color from yellow to red to brown and finally, to black. This stage can take anywhere from 2 to 27 days, depending on temperature, with faster development occurring at higher temperature.

Finally, the adult fly emerges from the pupal case. The average fly is about 6 to 7 millimeters long. In less than two weeks, newly emerged female flies can start laying eggs.

The Life Span of a Fly

In the Pixar movie, “A Bug’s Life”, a disgruntled fly said, “I only got 24 hours to live, and I ain’t gonna waste it here!”. So, flies live for 24 hours, right? We heard it straight from the fly’s mandibles.

Wrong.

Some may be shocked to learn that cartoons are not always accurate.

So, what’s the real story? How long do flies live?

Flies actually live way longer than 24 hours. In fact, they typically live anywhere from 15 to 25 days and can live for up to two months, as long as food is available. Their life span is highly dependent on ready access to sugar, more so even than manure.

Temperature is also another factor. Adult flies thrive in cooler temperatures.

Given the number of eggs they can deposit in just a few days, the speed with which they mature, and their surprisingly long life span, it’s easy to see why there always seem to be more flies.

2 Comments

Carol courtney

I have a caravan in wales and about october i went to stay and opened the door and found loads of them coming out from the cracks inside, not in the van but the door, any idea when they will vacate, they freak me out…

    InsectCop

    As can be read in this article, a fly will usually live around 15 to 25 days, with some making it up to two months, however, it doesn’t mean that will be the extent of your problem since they do reproduce. You can find out more about their life cycle and over-wintering in this article. With all this in mind, it might be a good decision to get rid of them instead of waiting for them to leave on their own since it’s hard to say when that might happen. You can try using insecticides, fly traps, etc.
    Also, don’t forget to make sure there are no food sources left in the caravan for them to feed on since those are not only attracting but also keeping them there.

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