How Long Do Gnats Live For?

  • Written By Dan Edwards on February 2, 2021
    Last Updated: February 2, 2021

You’re enjoying a family cookout at the height of summer. The burgers are on the grill, the kids are playing and you’re knocking back a cold one. Everything seems perfect — until a swarm of gnats arrives.

It’s been the same story for the past few weekends, with these tiny flying insects ruining a perfect evening. Exasperated, you wonder to yourself — aren’t they going to die off soon? Well, the actual lifespan of a gnat may come as a shock.

Gnats live for 40 days on average. Key factors affecting the lifespan of a gnat are:

  • Species
  • Seasons
  • Temperature
  • Access to food and water
  • Pesticides

Definition of Gnat Lifespan

The name ‘gnats’ covers a wide variety of insect species, including family groups such as:

Despite some familial and behavioral differences, they all live for a similar amount of time. 

The confusion arises, however, on when a gnat becomes a gnat.

These small creatures go through four different stages in their lifespan — egg, larva, pupa and adult. This entire process, from being an ovum through to dying as a flying insect, takes on average about 40 days.

Egg Stage — 4 to 6 Days

Dependent on their species, gnats lay their eggs in different locations — the fungus gnat in soil, midges (Chironomidae) in water, and eye-gnats in the sand.

Research shows that, despite the different familial groups, they produce a similar number of ova — typically between 200 and 400.

These eggs are round, less than one-tenth of an inch in diameter and can range from pure white to dark brown.

After six days, the eggs hatch.

Larva — 12 to 14 Days

Gnat larvae are voracious eaters, consuming vast amounts of food to grow and store the energy for their pupation stage.

Their meals of choice depend on the species. Fungus gnats, as the name suggests, typically consume fungi in moist soil. If you have them in your houseplants, they can often eat the roots of young and immature plants.

For gnat larvae living underwater, they munch through rotting debris, but equally, become a foodstuff themselves, being a delicacy for fish.

The larval stage usually encompasses about two weeks. Studies show that in certain conditions — such as lack of food or seriously cold water — this can take as long as four weeks.

Pupa — 7 Days

In the third stage of the life cycle, the larva forms a hard outer layer known as the pupa

Inside, the transformation into the adult — imago — begins as the young gnat grows wings, a three-part body and legs. In general, this takes about seven days.

Adult — 10 Days

The adult gnat emerges from the pupa, dries out its body, and can then fly.

Almost immediately, they’re sexually mature, meaning that they can mate and then create a second generation.

The bottom line: Overall, the total lifespan of a gnat is around 40 days, but only spends a quarter of those as an adult.

Factors Affecting the Lifespan of a Gnat

The above explanation of the gnat’s life-cycle assumes perfect conditions for reproduction and growth. However, external factors can affect this process.


Gnats are most abundant during periods of warmer weather, typically early spring through to late summer, often seen from May to August. Geographical location plays its part; those in the Western and Southern states will ‘enjoy’ a more extended gnat season.

Cold weather can equally affect the lifespan of a gnat. Contrary to what you may believe, it doesn’t always make it shorter — it can elongate it.

Scientists explain that gnats contain antifreeze proteins, protecting them from icy conditions that would otherwise end their life. Gnat adults are still able to reproduce and lay eggs.

The problem arises, though, in where they can lay them. If there’s insufficient access to unfrozen water or soil — dependent on species — the eggs may never hatch.

If the ova can be laid and they become larva, their lifespan can extend. They can remain in this wriggling form for an elongated period without turning into a pupa, which would be otherwise destroyed from cold conditions.

Recent studies from the Pirbright Institute also indicate that climate change is affecting the seasonality of gnats. Certain species have experienced an increase of 40 days to their primary reproductive period. This means you’re probably going to see more of these creatures as the years pass.

Access to Food and Water

Gnats have two things on their minds — sex and nourishment.

As they hang around together, sex isn’t usually a problem. It’s akin to being in a nightclub, 24/7.

Nourishment is an issue, though. Without sufficient access to food or water, they’ll die or relocate.

Depending on their species, gnats consume decaying vegetable matter, other insects or plants. If these flying critters are an issue in your home or garden, removing their food and water sources is often an effective method of reducing their numbers — and their lifespan.


Research from the Yale School of Forestry and Environmental Studies makes alarming reading. It explains that in some regions of Europe, insect numbers, including gnats, have declined by 72 percent — in the USA, by 40 percent.

Scientists blame this reduction on the overuse of pesticides, the abundance of monoculture and habitat destruction. 

Gnats can indeed be annoying. However, they’re also highly effective pollinators, essential for our food crops.

The next time you’re pondering about destroying your gnat problem — think twice.


The total lifespan of a gnat takes around 40 days; however, as an adult, they don’t enjoy much more than ten days to indulge in reproduction and eating.

The next time you see one buzzing around your head, and you’re thinking of swatting it, take a moment. Consider the remarkable journey this creature has already made and that its days on this planet are much shorter than yours.