Culturing Fruit Flies

Background and General Information on Fruit Flies

Fruit flies have long been the staple food source for dart frog keepers. Many different types of poison dart frogs have been raised from froglet to breeding adult on nothing but fruit flies. It is always a good idea to supplement your dart frogs diet with different food sources, but fruit flies can be a reliable inexpensive food source for your dart frog collection. They can also be used to feed some of the smaller geckos, especially as hatchlings.
Fruit flies are available in a variety of different species and genetic variations of species. Each type can vary in ease of culture and productivity. For this sheet all information concerns the Drosophila melanogaster. This is a small fruit fly with a short life cycle. It is available in a variety of flightless forms. Each is a specific genetic mutation which when crossed with a different mutation will produce many or all normal fruit flies. This means that if you have fruit flies from two different sources, you need to avoid mixing them together.
In normal production, at the appropriate temperature (75 to 80 degrees F is ideal) the time from setting up (inoculation) of the culture to the first good hatch of flies should be about two weeks. These flies should be left in the jar for a day or so, so they can lay the eggs for another generation. The flies are sexually mature at about 12 hours from hatching.

Don't allow large numbers of flies to remain in the culture for more than a couple of days, as the waste and load on the culture can sometimes be too much, and the flies can suddenly die, ruining the culture. If need be, you can dump flies into a cup and put a lid on it, then put it in the freezer to dispose of unneeded flies.
New cultures should be set up exclusively from freshly hatching cultures. This cuts down on the risk of mite transferal, as well as mold. Mites can overwhelm your cultures, and if this happens you will need to clean everything (shelves, and surrounding surfaces) and get new flies. It might help to use a new area for a while to prevent a reoccurrence of mites. Generally speaking, good husbandry and avoidance of contaminated cultures will prevent mite out breaks.

Mold is another problem, and it can be harder to deal with. In particular black mold is hard to get rid of. The mold spores, once released into the air, seem to linger forever, infecting new generation after new generation, in some cases. For this reason I recommend discarding cultures which have black mold in particular, without opening them. Once again the simplest solution to problems with either mold or mites is to get new flies, and clean everything while waiting for the new flies. You can also move your culturing and storage area temporarily.

Culturing Fruit Flies
First take a cup lid, and use a pair of scissor with a sharp tip to cut a hole in the lid, similar to the one that was in the cup lid that your started culture came with. Take a clean 32 oz deli cup, and measure out a third cup of media, which is placed in the bottom of the cup. Now add a scant half-cup of water to it. De-chlorinating your water will probably make a difference in increasing production, especially if your water supply is heavily chlorinated. Immediately swirl the water and media to mix the two together. Now add about two dozen flies, more if you have them. I place a double folded paper towel over the cup and put the lid on. No yeast is needed. Also, your culture that came in your starter kit may have had a paper towel down in the culture. This was put there to prevent the media from shifting around too much during transit to you. I don't recommend that you use the paper towel in your cultures at home, I don't think it is needed.

The culture should start producing new flies in about two weeks, and produce for about a month. The heaviest production will be in the first week or so of hatching. Once again don't forget to use some of these flies to start your new cultures with. You will probably need about one culture for every three dart frogs, and you should have some extra. Set up new cultures regularly, until you have too many going, then allow the number of new cultures to settle to a number, which will sustain your collection of dart frogs. Due to the two-week cycle of the flies you should probably set up the cultures every two weeks. As the cultures mature, and then expire, you can wash them out thoroughly and reuse them or throw them away. Also during the last half of the cultures life it may be necessary to add some more water to it, to avoid it drying out.

A word on cup lids and the holes you will be cutting in them. The size of the hole has a good deal to do with how well the culture does. Specifically the lid hole determines how much water evaporates from the culture, and whether your cultures are too wet or too dry. This is further influenced by the humidity in your home, which will change from one season to another in most cases. If you find that the paper towel that you are using to cover the culture is getting to wet, then you should remove that paper towel, and replace it with a dry one. Then cut your hole a slight bit bigger. You may also experience the opposite problem, the culture may become dry and crusty, sometimes as early as one week after you set it up. This may be due to your lid hole being too large. Try making the hole smaller. If you don't have a new lid, make the lid hole smaller with tape. We also offer lids which have holes in them, with a fabric coating over them. These work well, but its not easy to adjust the amount of air flow into the cups. You can try using tape again to cut down on the ventilation.

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