Fruit fly larvae: what they look like, where they live, and what to bin
Fruit fly larvae are dirty-white maggots about 2.5 to 5 mm long, living in the soft top layer of something fermenting. Because they stay near the surface, a bad patch on firm fruit can be cut away. The larvae worth worrying about are the ones that are not in the fruit bowl.
By The Pest GuyLast updated
The short answer
If you can see them, you have found one source. The job is the ones you cannot see.
Fruit fly larvae are very small, dirty white and maggot-shaped, about 2.5 to 5 mm long, with no legs and no eyes. They live in the top layer of whatever is fermenting and feed on the yeasts growing in it. As they eat, they turn the food into a semi-liquid mess, which is usually how you find them: a banana that has gone runny, or an onion at the bottom of the bag that has collapsed.
That surface feeding is the useful part. The University of Kentucky's entomologists say it means damaged or over-ripe parts of fruit and veg can be cut away without throwing out the rest. So a firm apple with one soft patch can be cut and kept. Anything soft all the way through goes in the bin.
Then the harder part. One female lays up to about 500 eggs, and full-grown larvae leave the food to pupate somewhere drier. So the next generation may already be off the fruit, or in a place you have not looked: a bag of potatoes, the recycling, a damp mop, a slow drain. If you are not sure how they got in at all, where fruit flies come from covers how they get into a house in the first place.
Is it a fruit fly larva? Four that get mistaken for each other
Small white or brown maggots indoors come from at least four different flies, and each one points at a different source.
| Larva | What it looks like | Where it lives | What it points to |
|---|---|---|---|
| Fruit fly | About 2.5-5 mm, dirty white, maggot-shaped | The soft top layer of fermenting fruit or veg, bin bottoms, mops, drain slime | Something sweet or fermenting has been left too long |
| Fungus gnat | About 6 mm, white and slender, with a shiny black head | Moist potting soil, feeding on roots and fungi | An over-watered houseplant |
| Phorid fly | 4-10 mm, brown, paler in the middle, can look banded | Any moist decaying material, including drain pipes and vase water | Decay somewhere less obvious than the fruit bowl |
| Drain fly | Hidden inside the slimy film it feeds on | The film in sink and floor drains, and fridge drip trays | A drain that needs cleaning, not the fruit |
Texas A&M AgriLife Extension, Michael Merchant, "Indoor Flies and Their Control" (ENTO-050); fruit fly row from the London Borough of Waltham Forest "Fruit flies fact sheet". Read 2026-10-06.
The quickest tell is where you found them. Larvae in the soil of a houseplant, with a shiny black head, are the fungus gnat, and a fruit fly trap is the wrong tool for that. The difference is set out in fruit flies vs fungus gnats, and flies coming out of plant pots has the fix for the pot.
Bigger maggots in meat, a meat wrapper or the general waste bin are a different fly again. Bluebottles breed on meat, offal and excrement, and that is a job covered in flies in the house. This table tells you what each kind usually means. It cannot tell you what is in your bin, and a description never could.
From egg to fly in about a week, and what slows it down
The whole cycle is fast in a warm kitchen. Temperature is the one lever you control.
| Stage | What it looks like | Where | How long |
|---|---|---|---|
| Egg | About 0.5 mm long. Up to about 500 per female | On the surface of rotting fruit and vegetables | Hatches after 12-15 hours at 25 °C |
| Larva (maggot) | About 2.5-5 mm, dirty white, legless, maggot-shaped | Feeding near the surface of the fermenting food, which turns to a semi-liquid mess | About four days at 25 °C, moulting twice |
| Pupa | Brown and cigar-shaped, glued to a surface | Somewhere drier. Full-grown larvae leave the food to pupate | About four days at 25 °C |
| Adult | About 2.5-5 mm, most species red-eyed | On ripe or fermenting fruit, where it lays | Mates within a few hours, starts laying about 24 hours later |
London Borough of Waltham Forest, "Fruit flies fact sheet"; Cornell CALS Integrated Pest Management, "Fruit Flies"; Drosophila melanogaster laboratory development figures as summarised on Wikipedia. Read 2026-10-06.
Two lines in that table change what you do. The first is the pupa. A full-grown larva leaves the food for somewhere drier and glues itself down, so binning the fruit late can leave the next batch behind. Wipe down the shelf and the bowl where the fruit sat, as well as getting rid of the fruit.
The second is the adult. It mates within a few hours of coming out and starts laying about a day later. Every fly still in the room is a fly that can put up to about 500 eggs into the next ripe banana, which is why where fruit flies lay their eggs matters as much as where the larvae are now.
| Temperature | Egg to adult | What it means |
|---|---|---|
| 28 °C | 7 days | The fastest it goes |
| 25 °C | 8.5 days | Waltham Forest gives 8-10 days in summer |
| 30 °C | 11 days | Slower again, from heat stress |
| 18 °C | 19 days | More than twice as long as at 25 °C |
Drosophila melanogaster egg-to-adult development times at controlled temperatures, as summarised on Wikipedia from the standard Drosophila laboratory references. Read 2026-10-06.
Drop from 25 °C to 18 °C and the cycle more than doubles, from 8.5 days to 19. Waltham Forest Council's advice follows from that: keep food they like in cold storage wherever you can, because the cold slows the larvae down. A fruit bowl on a warm worktop is the fastest place in the house to raise them. The fridge is the slowest.
Those are figures for the flies, not for how long your problem lasts. That depends on how long the source stays put, and on how long fruit flies live once they are adults.
Should you throw away fruit with fruit flies?
It depends on what the fruit looks like inside, and the answer comes from where the larvae feed.
Flies on the fruit means eggs may be on the fruit. Females lay on the surface of rotting fruit and veg, and the larvae that hatch stay near the surface to feed. Kentucky's fact sheet draws the practical line from that: damaged or over-ripe portions can be cut away without discarding the remainder.
In practice that sorts your fruit bowl into three piles. Firm fruit with no soft spots is fine; move it to the fridge. Firm fruit with one bruised, wet or split patch: cut the patch out with plenty of margin and use the rest soon. Anything soft, leaking or runny all the way through goes in an outside bin, because that is the semi-liquid mess the larvae make, and they are all through it.
The reason to cut generously is the one real health point. Texas A&M AgriLife Extension notes that eating food infested with fruit fly larvae has been reported to cause stomach upset, diarrhoea or intestinal myiasis. Fruit flies do not bite, so eating them is the risk worth managing, and whether fruit flies are harmful covers the rest of it.
Check what you keep in bags as well. Waltham Forest's fact sheet singles out potatoes and onions, which tend to be bought and stored in quantity: one rotten one at the bottom of the bag is enough to support a sizeable infestation. If you have binned every piece of fruit and the flies are still coming, that bag is the first place to look.
Where else the larvae live, and how to find them
They need very little. Kentucky's entomologists put it at a moist film of fermenting material, and a kitchen has plenty of those.
The places the extension services name, in a house:
- The wet bottom of a kitchen or food bin, especially where a liner has leaked.
- Bags of potatoes or onions, from one rotten one at the bottom.
- Recycling with unrinsed wine, beer or fizzy drink bottles and cans.
- Damp mops, brooms, dish cloths and cleaning rags that have soaked up food or drink.
- Loose lids on vinegar, wine, beer or cider.
- A slow or rarely used sink, bath, shower or floor drain with slime built up above the water line.
The drain is the one you cannot see into. Larvae there live in the slime above the water line, and an overnight bag over the plughole tells you whether that is where yours are. If it is, the slime is what needs cleaning out.
Kentucky is blunt about the rest: unless the breeding sites are removed or cleaned, the problem will continue. That is also why spraying fruit flies only buys time, and Texas A&M says the same of traps and sprays alike. If the source is still hiding after all that, finding the source in the house goes room by room.
A trap belongs alongside the search. Texas A&M points out that a bait trap helps you pinpoint the source and shows whether the clean-up is working, as well as cutting the numbers while you look. What makes a fruit fly trap catch flies and keep them is mostly about the way out, and the one below is built around that.
The flies in the room are laying the next batch
Binning the fruit ends the larvae in it. It does nothing about the adults already flying, and each of those mates within hours and starts laying about a day later. This is a cider vinegar trap you stand next to the fruit bowl or the food bin to catch them while you clear the source. It catches flies, never larvae, so it is the second half of the job.
What I’d use
Reusable cider vinegar trap
Escape-proof fruit fly trap
A two-part cup and lid you fill with about 25 ml of cider vinegar and stand by the fruit bowl.
Eight slots in the lid feed a funnel that drops flies through one 4 mm hole into the dark middle of the cup. The brightest points a trapped fly can see are pinholes too small to get through, set away from the real exit, so the way out is the place they are least likely to look.
- Ways in
- Eight slots in the lid, into one funnel
- Way out
- One 4 mm hole, under the solid centre of the lid
- Holds
- About 25 ml of vinegar, to the moulded fill line
- Size
- 6.7 cm across, 5.4 cm tall
- Refills
- None to buy. It runs on cider vinegar from the cupboard
Watch out for
- Vinegar and washing-up liquid not included.
- Made for fruit flies. Flies from a plant pot or drain need the source found.
- Tip, rinse by hand and refill once it fills up.
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About this resource
The weight on this page is carried by public sources rather than pest-control marketing: the London Borough of Waltham Forest's fruit fly fact sheet, the University of Kentucky's entomology fact sheet on fruit flies, Cornell's Integrated Pest Management programme, and Texas A&M AgriLife Extension's guide to indoor flies. The development times are laboratory figures for the common fruit fly at controlled temperatures, so read them as the shape of the curve.
The honest limit is identification. This page can tell you what each kind of larva usually means and where to look. It cannot tell you what is in your bin, and it would be doing you no favours by pretending otherwise from a description.
Common questions
Should you throw away fruit with fruit flies?
Not always. The larvae feed near the surface of whatever is fermenting, and the University of Kentucky's entomologists say that means damaged or over-ripe parts of fruit and veg can be cut away without throwing out the rest. So a firm apple with one soft patch can be cut and kept. Anything that has gone soft and runny all the way through goes in the bin, because by then the larvae have turned it into the semi-liquid mess Waltham Forest Council describes. Keep what is left in the fridge, which slows the next lot down.
How do you get rid of fruit fly larvae?
Take away what they are living in. Bin the fermenting food, then look for the other places they breed: the wet bottom of a bin, a bag of potatoes or onions, recycling with unrinsed bottles and cans, a damp mop or dish cloth, and the slimy film inside a drain. Kentucky puts it plainly: unless the breeding sites are removed or cleaned, the problem will continue. A trap catches the adults. It does nothing to larvae.
Are fruit fly larvae harmful?
Fruit flies do not bite. The risk is eating them. Texas A&M AgriLife Extension notes that eating food infested with fruit fly larvae has been reported to cause stomach upset, diarrhoea or intestinal myiasis. That is the reason to cut generously round a soft patch and to bin anything soft all the way through.
How long does it take for fruit fly larvae to turn into flies?
About a week in warm conditions. At 25 °C the eggs hatch in 12 to 15 hours, the larvae feed for about four days, and the pupa takes about four more, so egg to adult is roughly 8.5 days. At 18 °C it stretches to about 19 days. Waltham Forest Council gives eight to ten days in summer conditions.
What if I accidentally eat fruit fly larvae?
Texas A&M AgriLife Extension says eating infested food has been reported to cause stomach upset, diarrhoea or intestinal myiasis. Nothing I have read puts a likelihood on it. If you feel unwell afterwards, that is a question for a pharmacist or your GP, and the rest of the fruit goes in the bin.
What do fruit fly larvae turn into?
A brown, cigar-shaped pupa. When a larva is full grown it leaves the food for somewhere drier, glues itself to a surface and spends about four days changing inside the pupal case at 25 °C. What comes out is an adult fruit fly, which mates within a few hours and starts laying eggs about a day later.
How long after fruit flies lay eggs do maggots appear?
Within a day. The eggs are about half a millimetre long and hatch after 12 to 15 hours at 25 °C. A cooler room slows that down, which is why the fridge is the slowest place for them to develop.