When many people hear “fruit flies”, an image comes to mind of rotten fruits and vegetables under a cloud of small gnat-like bugs, needing an immediate trip to the garbage can. However, fruit flies are a valuable staple in the diet of Poison Dart Frogs and other amphibians, baby lizards, and many fresh water fish. There are flightless and wingless fruit flies, and they can easily be cultured at home, at minimal cost, providing the pet owner with a virtually free and endless supply of meals for their pet.
Drosophillia is the genus to which fruit flies belong, and the most common species of feeder flies are D. melanogaster and D. hydei.D. melanogaster are smaller flies, and can be found in both flightless and wingless varieties. D. hydei are a larger species, and can be found commonly in smaller Gold and larger Black varieties. Choose which species to feed to your pet based on size. Most fish can eat either size, as can the larger species of lizards and amphibians. If you have some of the smaller thumbnail Dart Frogs, you’ll probably want to only culture D. melanogaster.
A group of flies in a container is referred to as a “Culture” and the process by which one creates new groups of fruit flies from which to feed is called “culturing”. One culture can start to produce fruit flies in as little as one week, and can keep producing for 6-12 weeks, depending on environmental conditions and species. The number of animals one culture can feed depends solely on the animal and it’s consumption rate. For example, one culture can easily feed 20 Poison Dart Froglets over the course of it’s production, but when the frogs become adults, it may require 3 cultures to maintain your frogs.
The components of a culture are an escape-proof container with a breathable lid, “media”, and something to provide more surface area for the fruit flies. There are several variations on all of these components. Sometimes commercially available products are best, yet often, homegrown solutions are optimum.
While there are commercially available plastic containers with breathable lids, mason jars can be used, the mouths covered with muslin, and only the ring used to hold the muslin in place. However, feeding is much easier with the commercially available “Fruit Fly Culture Cups”, as the flies tend to escape more often when returning the muslin and securing the ring than they do while snapping on a plastic lid. The Culture Cups are readily available online, and incur a nominal cost.
“Media” is the hobbyists’ term for the substrate in which the females lay eggs, which also serves as food for larval fruit flies. There are many commercially available “media mixes”, but this is one instance where you can make your own for less and much more conveniently. (See my article on making home-made fruit fly media.)
Increased surface area is needed so that the fruit fly larvae have a place onto which to crawl out of the media and pupate, as well as a place for the adult fruit flies to perch until you feed them to your pet. The two most common ways to increase the surface area in the container are to add either a coffee filter or some Excelsior. Excelsior is merely aspen shredded into long string-like fibers, and is available at craft and packing stores. Coffee filters will work in a pinch, but the Excelsior is preferred.
Now that the basics are covered, gather supplies for culturing. You’ll need:
1. an existing culture, available at many pet stores, or you can order online
2. culture cups and lids (32oz is common, adjust recipe as needed for smaller containers)
3. media- about 1/3 cup per 32oz culture
4. hot water and white vinegar 1:1 ratio
5. surface area substrate
To make your culture:
In a large bowl, mix 1/3 c. media with 1/3 c. water/vinegar mixture. The vinegar prevents mold from growing in your cultures. Let media stand and absorb water. Continue adding water until the mixture is very moist, but still holds together well, somewhat like warm peanut butter. Let stand and check consistency after 5 minutes. If more water is needed, add in very small amounts. Remember, it’s easy to add more water, you can’t remove water!
Scoop media into the bottom of culture cup. Tap the cup on the counter/table top to distribute evenly on the bottom of the cup. Separate out a ball of Excelsior and separate the fibers by “combing” through it with your fingers. Roll lightly between your palms until it forms a ball that will fit in on top of the media and take up the bulk of the space in the culture cup and place lightly onto media. If you’re using coffee filters, fold or crumple them, and place lightly on top of media.
Have your lids at the ready for the next step.
Tap the existing fruit fly culture to make the flies fall to the bottom of the cup. Open the existing culture, and tap some fruit flies into the new culture. 20 or more flies should be added to the new culture. Tap each culture on the counter/table as needed to keep flies from escaping. Place lids on each culture. Label your new culture with the date and species, and place in an area that will get partial or indirect sunlight, required for life cycle and production of vitamins. In 1-2 weeks you should see fruit fly larvae writhing around in the media, climbing out, and pupating on the surfaces of the culture cup and Excelsior. Soon your cultures should be booming with fruit files.
Once your new culture is booming with flies, make another new culture. Keep repeating the cycle, and you will have an endless supply of food for your pets.