Fruit flies are a great staple food for dart frogs, small geckos, surface-feeding fish, and more. Here is how to culture fruit flies as a live food.

Types of flightless and wingless fruit flies

There are two species of fruit fly commonly cultured as live food. The smaller of the two is Drosophila melanogaster, often known as “melanos” or “melos” for short. They come in several varieties. One, called apterous or wingless, has basically nonexistent wings, and can only walk or make very short hops. Another variety has wings, but they do not function properly. Their wings can move and make a tiny buzzing sounds, but they can only make short, erratic, wing-assisted hops (about one inch at a time), so they are much more manageable than fully flighted fruit flies. Having cultured both types, I prefer to work with the wingless ones, as they are slightly easier to handle.

The other species of fruit fly cultured as a live food is Drosophila hydei. This species, while still very small, is considerably larger than D. melanogaster. This species has large, clearly visible wings. The wings are not functional, however. There is a wild-type and golden variety of D. hydei. Because this species of fly is larger, it is a great food for somewhat bigger fish, frogs, geckos, and so on.

Fruit fly Culturing Supplies

Fruit flies need to be cultured in an escape-proof container. This can be as simple as a glass jar with a paper towel as a lid, secured with a rubber band. However, I prefer to use 32-oz. deli cups, with ventilated lids sold specifically for keeping fruit flies and other small creatures. They are convenient, especially if you have more than just a few cultures, and last longer than the somewhat fragile paper towels:

Fruit flies will live and breed much better if they have additional surface are in the culture container. In my experience, the best way to provide this is with excelsior, which is finely shredded aspen wood:

Once you have added the culture medium to the container (more on that below) take a loose tennis ball- or oange-sized ball of excelsior and push it lightly into the fresh culture medium.

Now for the culture medium, which serves as food for the flies and larvae. You can buy convenient premixed fruit fly culture medium. It is very simple to mix and use:

You can also make your own fruit fly medium. There are many recipes out there. Here is the recipe I currently use. This makes enough medium for 1-2 32 oz. deli cup cultures.

2/3 cup plain dry potato flakes

1 teaspoon green pea powder

1 teaspoon nutritional or brewer’s yeast

1/2 teaspoon pure Spirulina powder

1/4 tp 1/2 teaspoon methyparaben (to protect against mold)

1 tsp brown sugar

A pinch of active dry yeast

Approximately 2/3 cup slightly warm water, preferably dechlorinated or filtered

Thoroughly mix the potato flakes, Spirulina, green pea powder, nutritional yeast, and methylparaben. Pour into the bottom of the culture container. Dissolve the teaspoon of brown sugar in the water, and then pour half of the water into the dry mix. Stir. If it looks lumpy, add a little more liquid. Stir and add water as needed until the medium is of a smooth consistency, such that it will flatten if you tap the bottom of the container against a Tabletop, rather than remaining lumpy. Sprinkle a pinch of active dry yeast on the surface. Add a loose ball of excelsior, about the size of a tennis ball. Cover with the vented lid and allow to set for several minutes, then add about 50 flies. Keep between 70 and 80 F. Within a few days, you should see larvae crawling around near the surface of the medium. Within about 10 days to 2 weeks, (D. hydei take a little longer than D. melanogaster) you will have a new crop of flies.

Harvesting Flies

Harvesting from your fruit fly cultures regularly is probably the most important maintenance you can do for the life of the culture. If too many flies build up inside the culture, they will cause the culture to crash and die much more quickly. To harvest, hold the culture at an angle over a collection container and tap the culture rapidly. This will ensure that most of the fruit flies end up in the collection container rather than crawling up and out the top of the culture container. Holding the container at an angle also helps prevent the culture medium from spilling out. If you are feeding fish or insects, you can immediately feed out the collected flies. If you are feeding them to amphibians or reptiles, you will want to dust them lightly with a vitamin and/or mineral supplements. One of my favorites to use is Repashy Calcium Plus:

Troubleshooting a Fruit Fly Culture

If you set a culture up correctly, and harvest from it regularly once it starts producing, it should produce flies for several weeks. A cultire that is more than a month old should be discarded, or mites may begin to infest the culture. If you find a culture containing mites, throw it away immediately.

Mold can be an issue in fruit fly cultures. I find I have few if any issues with mold by adding food-grade methylparaben as indicated in the recipe above. Commercial media mixes already contain mold inhibitors, so there is no need to add any.

Finding the right quantity of liquid to add to the culture medium when you initially mix it is crucial. If you add too much, the culture will tend to get soupy, especially as it matures, and then flies tend to drown. Harvesting is also more difficult, as tipping the culture container will cause the medium to slosh up the sides. If you add too little, the culture can dry out, and/or mold. The exact quantity of water varies depending on temperature and humidity levels where your culture resides. As a rule of reminder, when you first make the medium, it should be soft enough to smooth out when you tap the bottom of the culture container on a table or counter, it should flatten out, but remain fairly firm…not soupy. You can add a little more water if it is too firm, or some more potato flakes if it is too soupy.

Starting New Cultures

It is important to start new cultures from existing cultures regularly. The best time to start a new culture is when the existing culture is at it peak…several days to a week after it has been producing flies. This ensures you have plenty of healthy, mature flies, and reduces the risk of mites, which tend to show up in older cultures. I try to make up new fruit fly cultures every week or two so I have cultures in various stages at any given time without fear of running out.

For more on culturing fruit flies, check out my ebook and my video:

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