Look: white, segmented and legless with black mouth hooks; up to about 4–5 mm long (Vanderbilt; Wipfler et al. 2013). How long: the larval stage lasts about 3.9 days at 25 °C (77 °F) and 4.8 at 22 °C, over three instars, then the pupa takes about 4.1–5 more days. Where: the moist surface of fermenting fruit, fruit-bowl juice, bins and drain slime (University of Kentucky; UConn).
Fruit fly larvae: what they look like
A fruit fly larva is a tiny, white, segmented worm with no legs and no eyes. Its narrow front end carries a pair of black mouth hooks — the "jaw hooks" it uses to rake food into its mouth — and it breathes through a pair of air holes (spiracles) at each end of its body (Vanderbilt University lab guide; Tyler). The body is see-through enough that you can often make out the dark gut and the white fat inside. Fully grown, a fruit fly larva is about 4–5 mm long and about 1 mm wide (Wipfler et al. 2013), a little shorter than a grain of rice.
Scientists usually call them drosophila larvae, after the fruit fly's genus. They spend almost all their time eating, burrowing through the soft surface of fermenting fruit and swallowing the yeast that grows on it. Unlike many insects, they never wander far: the University of Kentucky notes that larvae of the small household flies "have limited movement" and stay in the rotten fruit, drain or organic matter where they hatched.
Fruit fly larvae size
Size depends on age. In a 1984 study at 25 °C, larvae averaged about 1.55 mm a day after hatching and about 4.7 mm three days after hatching (Godoy-Herrera et al. 1984). So anything under 2 mm is a young larva, and anything around 4–5 mm is close to the end of its feeding life. A plump, creamy maggot of 8–10 mm is too big to be a fruit fly larva; house fly maggots reach about 10 mm (Virginia Cooperative Extension), and adult house flies live a few weeks (house fly lifespan).
Drosophila larvae stages (instars)
So where do fruit fly larvae live? In the food itself, for their whole larval life — and there they grow in steps. Insect skin doesn't stretch, so a growing larva has to shed it. Fruit fly larvae moult twice, which gives three larval stages called instars — the fruit fly instars you see listed in lab guides. Each moult also replaces the mouth hooks, and both the larva's size and the number of teeth on its jaw hooks tell you which instar it has reached (Vanderbilt). FlyBase gives the timings at 25 °C: the first instar runs from hatching at about 24 hours to the first moult at about 49 hours after the egg was laid, the second to about 72 hours, and the third to about 120 hours.
| Instar | Size | Lasts at 25 °C | At 22 °C | At 18 °C | What it's doing |
|---|---|---|---|---|---|
| 1st instar | Up to about 1.5 mm (1.55 mm on average a day after hatching) | 1 day | 1.3 days | 2.2 days | Hatches from the egg and starts feeding in the surface of the food |
| 2nd instar | Between about 1.5 and 4.5 mm | 0.9 days | 1.2 days | 2 days | Moults, keeps burrowing and eating; jaw hooks gain more teeth |
| 3rd instar | About 4–5 mm long and 1 mm wide (4.7 mm on average 3 days after hatching) | 2 days | 2.4 days | 4.1 days | Eats and grows the most, then stops feeding and climbs out to pupate |
Durations at 22 °C and 18 °C use the Bloomington Drosophila Stock Center's egg-to-adult times, shared out in the same proportions as at 25 °C. All three fruit fly larvae stages together last about 3.9 days at 25 °C, 4.8 days at 22 °C and 8.3 days at 18 °C. The third instar is the longest and the one you are most likely to notice.
The wandering stage
Near the end of the third instar, a larva stops eating and changes its behaviour. Instead of staying in the moist food, it crawls up and away from it to find a relatively clean, dry place, stops moving and pushes out its front spiracles, ready to pupate (Vanderbilt; Tyler). In a lab test, late third-instar larvae readily crawled onto a dry surface that younger larvae kept turning back from (Godoy-Herrera et al. 1984). This "wandering" is why you find larvae on the side of the fruit bowl, the rim of the bin or the kitchen wall, a short way from the food.
How long until fruit fly larvae become flies?
From hatching, about 8 days at 25 °C: roughly 3.9 days as a larva and 4.1 as a pupa. At 22 °C it is about 9.8 days and at 18 °C about 17. Put another way, fruit fly larvae to adult takes a little over a week in a warm kitchen. So the honest answer to how long do fruit fly larvae live is "a few days" as larvae — and then, unless something stops them, they turn into the next batch of flies. The calculator's larva-to-fly timer gives you the dates from the size of the larvae you've found; the fruit fly pupa timer takes over once they've formed brown cases.
Fruit fly worms and maggots: what people are really seeing
Most people who find "worms" in their fruit bowl are looking at fruit fly worms — the larvae. They are maggots in the true sense: "maggot" is simply the everyday word for a fly larva, and extension educators describe the fruit fly's second life stage as "larva (called a maggot)" (UConn Extension). So yes, those are fruit flies' maggots; they just aren't the large maggots people picture from bins and compost heaps.
Several other small, white, legless larvae turn up in homes and gardens, and they mean different things. The two comparisons people ask about most — fruit fly larvae vs drain fly larvae, and fruit fly larvae vs fungus gnat larvae — come down to where the larvae live and whether you can see a dark head. Here is how they compare:
| Larva | Where you find it | Size | Look | Source |
|---|---|---|---|---|
| Fruit fly larva (Drosophila) | Overripe fruit, fruit-bowl juice, bins, drain slime | Up to 4–5 mm | White, segmented, legless; black mouth hooks; no eyes | Vanderbilt; Wipfler et al. 2013; UKy |
| True fruit maggot (Tephritidae: apple maggot, blueberry maggot, olive fruit fly) | Inside fresh fruit on the tree or bush | 5–6 mm (blueberry maggot) | Creamy or yellowish white, black mouth hooks; usually one per fruit | UF/IFAS IN198; UC IPM |
| Drain fly larva (moth fly) — drain fly life cycle | Slimy film inside drains; standing water | Not given in our sources | Slender, white to creamy brown, distinct head, breathing tubes at the tail | UF/IFAS EENY-716; UKy |
| Fungus gnat larva — gnat life cycle | Moist potting soil and organic matter | Not given in our sources | Whitish-to-clear, legless body with a shiny black head | UC IPM 7448 |
| House fly maggot — house fly life cycle | Garbage, dung and rotting material | About 10 mm when grown | Yellowish-white, tapered head with no head capsule | Virginia Cooperative Extension |
True fruit maggots in garden fruit
Gardeners sometimes find maggots inside apples, blueberries, cherries or olives picked straight from the plant. These are usually not Drosophila but Tephritid fruit flies — a separate family that includes the apple maggot, the blueberry maggot and the olive fruit fly. The female lays eggs inside sound, ripening fruit; the blueberry maggot, for example, lays a single egg per berry, and its creamy white larva grows to 5–6 mm before leaving the fruit to pupate about an inch down in the soil (UF/IFAS). Olive fruit fly larvae pupate inside the fruit in summer and in the soil in autumn (UC IPM). Unlike fruit fly larvae, these are crop pests rather than kitchen pests.
White worms in fruit that is still fresh and firm — strawberries, raspberries or blueberries — are usually a third kind: spotted wing drosophila, a Drosophila that lays inside ripening berries — see larvae in strawberries for the risk check and salt water test.
Signs of a fruit fly larvae infestation
A fruit fly larvae infestation is easy to miss, because the larvae are small and stay inside their food. Look for these signs:
- Tiny wriggling worms in liquid. The larvae are easiest to see in the pool of juice at the bottom of a fruit bowl (UConn Extension) or in the sticky film at the bottom of a bin.
- Fruit that softens and collapses from one spot, with a wet, fermenting patch under the skin where larvae are feeding.
- Larvae climbing walls. Fully grown larvae leave the food to pupate, so they appear on the sides of bowls, containers and bins (Tyler).
- Small brown cases stuck to a surface near the food — the University of Kentucky's fact sheet shows fruit fly pupae on a trash bag. See the pupa page to read what their colour means.
- New adults a week or more after you cleaned up, which means another breeding spot is still active.
Fruit fly larvae in trash and compost
Fruit fly larvae in trash live in the same moist, fermenting film as in a fruit bowl: juice from discarded fruit, the dregs in bottles and cans, and food residue on the bin's walls. One rotting potato or onion, a juice spill under the fridge or a recycling bin that is never cleaned can breed thousands of flies (University of Kentucky). Bigger, plumper maggots in an outdoor bin are more likely to be house fly maggots, which grow to about 10 mm (Virginia Cooperative Extension).
Fruit fly larvae in water, drains and sinks
Can fruit fly larvae survive in water? They are built for a moist surface, not for swimming. Fruit fly larvae breathe air through spiracles at both ends of the body (Vanderbilt), and the eggs have floats so they don't sink into runny food. Third-instar larvae can tunnel into food with very little oxygen for a while, but when researchers removed oxygen completely, half the larvae died within about an hour — far sooner than adult flies (Callier et al. 2015). We found no study that timed how long fruit fly larvae in water survive, so it isn't clear that soaking or flushing reliably kills them.
Fruit fly larvae in the drain and sink
Fruit fly larvae in drain pipes live in the slimy layer of food residue above the water line, especially in drains that are slow or seldom used (Iowa State University). The same goes for fruit fly larvae in sink overflows and the garbage disposal. Running water alone doesn't remove that film; scrubbing with a stiff brush does. If the worms you see are slender, greyish and hanging in water with a breathing tube at the tail, they are more likely drain fly larvae, which have breathing siphons and can trap air bubbles to cope with low oxygen (UF/IFAS) — the identifier above will tell you, and the drain fly lifespan calculator covers drain flies.
Are fruit fly larvae harmful?
Not in the way people fear. Fruit fly larvae don't bite, and the University of Kentucky describes fruit flies as mainly nuisance pests — although adults can carry bacteria and other disease-causing organisms onto food. Regulators treat fly larvae in food as an aesthetic problem: the FDA's Food Defect Levels Handbook sets limits such as an average of 4 or more larvae per 500 grams of canned or frozen drupelet berries, for defects it describes as natural or unavoidable and presenting no health hazard.
Did I eat fruit fly larvae?
Possibly — and so has almost everyone. If you bit into a piece of fruit and then found larvae, the food-safety view is that the larvae themselves aren't hazardous. The practical rules are to cut away damaged or over-ripe parts before eating, because that is where eggs and larvae are (University of Kentucky; FDA), and to rinse fruit under running water. If you feel unwell after eating spoiled food, that's a question for a doctor, not a fly identification problem.
How to get rid of fruit fly larvae
You get rid of fruit fly larvae by removing their food, not by spraying them. Extension services agree that the breeding source has to go, because insecticides only reach the adults (University of Kentucky; Iowa State University):
- Seal infested fruit in a bag and bin it outside, so wandering larvae can't crawl out and pupate in the kitchen.
- Cut away soft, damaged parts of fruit you want to keep; larvae feed near the surface (University of Kentucky).
- Wash the fruit bowl, the bin and any juice spills, including under the fridge.
- Scrub drains and the disposal with a stiff brush, then pour boiling water slowly (Iowa State). Test a drain by taping a clear plastic bag over it overnight (University of Kentucky).
- Wipe off brown pupal cases near the food, on walls and on bin bags — they will become adults in a few days.
- Refrigerate ripe produce to stop development, and trap leftover adults with cider vinegar and a paper funnel (University of Kentucky).
Once the source is gone, the remaining adults die within days; the fruit fly die-off timeline gives you the date.
How this fruit fly larvae tool works
What larvae is this? Each answer adds points to the larvae it matches in our sourced table: where you found them and what they look like count most (3 points each), then movement and size (2 each). Size never counts against drain fly or fungus gnat larvae, because we found no sourced length for them. The top score is the most likely match; confidence is "high" only when it scores well and clearly beats the runner-up, and a "Not sure" answer caps it at "medium". Drain fly and fungus gnat results link to the gnat calculator.
Larva-to-fly timer. Small larvae (under 2 mm) are treated as first instar, medium (2–4 mm) as second instar and large or wandering larvae as third instar. The tool takes that instar's place in FlyBase's 25 °C timeline, scales it to your temperature with the Bloomington egg-to-adult times — the same model as the life cycle calculator — and gives a range: from the larva being at the end of its instar to the very start. Dates are counted from today and rounded to the nearest day. The temperature must be 18–29 °C (64–84 °F).
Frequently asked questions
What do fruit fly larvae look like?
Tiny white, segmented worms with no legs and no eyes, a pointed front end with black mouth hooks, and up to about 4–5 mm long (Vanderbilt; Wipfler et al. 2013).
Are fruit fly worms the same as maggots?
Yes. "Maggot" is the everyday word for a fly larva, so fruit fly worms are maggots — just much smaller than house fly maggots, which reach about 10 mm.
How long until fruit fly larvae turn into flies?
About 8 days from hatching at 25 °C — roughly 3.9 days as a larva and 4.1 as a pupa — and about twice as long at 18 °C.
How long do fruit fly larvae live?
The larval stage lasts about 3.9 days at 25 °C and 8.3 days at 18 °C, across three instars, before the larva pupates.
Can fruit fly larvae live in water?
They breathe air and live in moist films, not open water. With no oxygen at all, half of third-instar larvae died in about an hour (Callier et al. 2015); survival in plain water hasn't been timed.
Why are there fruit fly larvae in my drain?
Fruit flies breed in the slime above the water line in slow or seldom-used drains and disposals. Scrub the drain with a stiff brush and pour boiling water slowly (Iowa State).
Are fruit fly larvae harmful?
They don't bite, and the FDA treats fly larvae in food as a natural, unavoidable defect with no health hazard. Cut away damaged fruit and rinse what you keep.
What is the difference between fruit fly larvae and drain fly larvae?
Fruit fly larvae are white with black mouth hooks and live in fermenting food; drain fly larvae are slender, white to creamy brown with a distinct head and breathing tubes, in drain slime and water.
What is the difference between fruit fly larvae and fungus gnat larvae?
Fungus gnat larvae have a shiny black head and a clear-to-white body and live in moist potting soil (UC IPM); fruit fly larvae have no visible head capsule and live in fermenting food.
Why are fruit fly larvae climbing the walls?
Fully grown third-instar larvae leave the food to find a dry place to pupate. Within hours they stop, harden and turn into brown pupal cases.
How do I get rid of fruit fly larvae naturally?
Bag and bin infested fruit, wash the fruit bowl and bin, scrub drains, wipe off pupal cases and refrigerate ripe produce — no pesticide needed.
What do fruit fly larvae eat?
The yeast and fermenting fruit in the top layer of their food. Because they stay near the surface, a damaged patch of fruit can usually be cut away and the rest kept (University of Kentucky).
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.