Flies are disgusting and the bane of so many people’s existence if you ask most people. It’s not surprising though, seeing as their notorious lifestyles aren’t exactly top secret. For instance, these dirty creatures love to perch on and live in really filthy places such as garbage, fecal matter, and even dead and decaying matter. And then these imps will still have the guts to perch on our pets, sometimes our food, and when they get really bold, our lips! Such gumption!

With the way that your yard never seems to be lacking on a constant supply of flies all year round, one might be tempted to think that these creatures are immortal, or at least, should be the ones mentioned when we talk about animals with nine lives. It just seems like they never die.

Well, it is true that it seems like they never die, but they actually do as we’re sure you probably already know. What you might not know the answer to, though, is this: how long do flies live? Today, you’re going to be learning more about flies, their life cycles, and their life spans. When we are done, you’d understand why flies seem to be ever-present, maybe it might help you deal with them a bit if you understand this fact. Who knows?

The lifecycle of a Fly

Flies are said to undergo complete metamorphosis; this means that their lifecycles contain a pupal stage; that is, from egg to larva to pupa to adult. Now, let’s see how the process takes place.

It begins with the female fly laying eggs. When we say eggs, do not think two or three or even twelve. Think 100 to 150 per batch: this is the average number of eggs laid by a female fly per time. However, this number might vary slightly depending on the size of the adult female fly. Some female flies can even produce up to five to six egg batches in a relatively short period, say a few days.

When the female wants to lay eggs, she prefers to find a dark, damp, and of course, filthy environment to lay her eggs. Places like under compost piles and manures are excellent options for her. Furthermore, for the eggs to hatch properly, they must remain moist.

Morphologically, fly eggs are usually whitish in color and are roughly 1.2 millimeters long.

After the egg stage, they metamorphose into larvae. At this stage, they measure about 3 to 9 millimeters in length. In warm weather, the metamorphosis from the egg stage to the larval stage occurs very fast, taking about 8 to 20 hours at the most. Larvae require high temperatures of within 95 to 100 degrees Fahrenheit to successfully change into maggots. If this temperature is steadily maintained, it will only take about 4 to 13 days for the larva to grow fully. For proper growth, larvae actually need a bit of manure and once they’ve grown to become maggots, they crawl away in search of cooler and dryer environs where they can now change again into pupae.

The pupal stage witnesses a lot of changes in the growing fly, both in shape and in color as well. In the first place, we see a change in color from yellow to red, then brown, and finally black. And then, shape wise, pupae differ slightly from larvae in that they appear a bit more rounded at both ends, unlike larvae that are cylindrical. At this stage, it only takes about 2 to 6 days, at a temperature range of 90 to 99 degrees Fahrenheit, for the pupa to fully develop and then transform into a full-fledged adult fly.

Adulthood is the final stage of the metamorphosis. And at this stage, the average fly averages about 6 to 7 millimeters in length. Size may, sometimes, differ according to sexes, though.

The Lifespan of a Fly

Yeah, in the Pixar movie, “A Bug’s Life”, a disgruntled fly said and we quote, “I’ve got 24 hours of living, and I ain’t gonna waste ‘em here!”. That seems pretty cut and dried, yeah? We should conclude that flies have a lifespan of 24 hours since we’ve heard from the horse’s mouth, right? Wrong. What you heard from was a fly’s mandibles—an animated one actually. So what’s the real story? How long do flies live?

Contrary to widespread rumor, flies actually live way longer than 24 hours. In fact, entomologists give the lifespan of a typical housefly to be about 25 days. So, usually, the lifespan of flies will last between 15 and 25 days. Of course, there are always exceptions to the rule, so it isn’t rare to find flies that have a lifespan of up to two whole months.

In spite of this though, flies can have an extended lifespan if a few factors are made available. Like all living beings, flies need food to survive, and if starved for two to three days, a typical fly will die quickly. Also, if a fly has a constant regular access to a supply of sugar, that will help to enhance the longevity of its lifespan.

Temperature is also another factor. Adult flies thrive in cooler temperatures when compared to warmer climes. Cooler temperatures, mind you, not cold climes.

As we mentioned earlier, the lifespan of these flies still varies with the presence or absence of certain factors such as climate, availability of food, and temperature.
Now, you know why flies appear to be ever-present.