I walked outside that morning and immediately noticed what looked like hundreds of tiny grains of rice scattered across the lid of my garbage can. My first thought was that a trash bag had somehow ripped open, but when I leaned closer, the little white pieces were moving. That was when I realized they weren’t grains of rice at all.

The unsettling answer is maggots—the larval stage of flies. Flies are strongly attracted to decomposing organic material, particularly food waste. Garbage cans provide an almost perfect environment because they can contain food, moisture, warmth, and odors that attract adult flies looking for somewhere to lay their eggs.

Seeing them covering the outside of the container doesn’t necessarily mean the eggs were laid on the lid. After feeding, some fly larvae naturally crawl away from the wet food source and search for a drier, protected location where they can pupate. That behavior can produce the disturbing sight of large numbers suddenly crawling over the sides and lid of a garbage can.

The infestation can also appear incredibly quickly. Warm conditions accelerate the fly life cycle, meaning a garbage bag containing meat scraps or other decomposing food can attract flies and produce visible larvae surprisingly soon. This is why the problem is particularly common during hot weather.

So those moving “grains of rice” aren’t rice, worms appearing mysteriously from the garbage, or some unknown parasite. They’re fly larvae, commonly called maggots. Emptying and thoroughly cleaning the bin, allowing it to dry, keeping food waste securely bagged, and keeping the lid closed can help prevent another outbreak. It’s disgusting to discover, but it’s also a very common consequence of flies gaining access to household garbage.