Fruit Fly Cultures Care, How To, Using and Making
Introduction: Fruit flies are the go to feeder insect for small carnivorous pet bugs, reptiles, amphibians and many other small pets. There are several varieties on the market but the main two are Drosophila melanogaster and Drosophila hydei. Though the care for these two species is the same, which one you choose depends on what you're feeding them to. In both cases, most of the varieties that are available online are not capable of flying like the wild fruit flies that visit your fruit basket in the warmer, summer and fall months.
A helpful video I made for YouTube that demonstrates the concepts on this page...
Fruit flies have a long history in this country as feeders and for studies in genetic inheritance in laboratories. We owe our wingless cultures of feeder Drosophila melanogaster to this science. The fruit fly is a model organism for these studies because they reproduce new generations very quickly, in as little as about 7 days. Cultures ship with adult flies and usually these have already laid eggs in the food media at the bottom of the cage. Often, larvae are already wriggling around through the half inch or so of food media at the time of arrival too. Within a week, eggs hatch, larvae grow larger and then pupate (little cocoons they paste to the sides of the container), and finally fresh adults emerge from these pupae/cocoons.
Both of the commonly available species of fruit flies on the market are able to climb up the smooth surfaces of glass and plastic tanks walls.
Drosophila melanogaster are the smaller of the two popular fly species on the mainstream hobby market. These tend to be genetically modified to be apterous (completely absent of wings). They are the go-to option for the smallest carnivorous pets.
Drosophila hydei have 2 to 4 times the mass of D. melanogaster and so they are the next step up for pets that have grown just slightly too large for the D. melanogaster. Most D. hydei cultures available for sale on the open market are genetically modified so that the musculature of the wings is inoperative. They have wings but they cannot fly. At best they can sort of hop around a little bit, making them highly attractive to your predatory pets.
Please feel free to email me with specific questions or suggestions for this caresheet.
Housing and Use: Fruit fly eggs and larvae live in the moist media at the bottom of the culture, while the adult flies tend to hang out on the dry excelsior that fills the airspace in the cup. Excelsior is also known as wood wool. It consists of spaghetti like strands of wood that that Any sort of container will do but one that is taller than wide is recommended. A lid that opens and closes easily helps to prevent flies from escaping while you are using the culture. A contain that is two to four times as tall as it is wide is best. The taller your container is in combination with the smaller the opening at the top, the fewer flies will be waiting for you at the top when you open it. Firmly tapping the bottom side of the culture down on a counter top a few times before you take off the lid will knock all the flies down to the bottom. They will crawl up in a matter of 3 or so seconds though, and so you should be ready to open the container as soon as you tap them down, or tap them down once again. Never leave the lid off your culture. And never feed off all the flies or they will not continue to lay eggs to make new larvae. A fruit fly culture should last about 4 to 6 weeks, on average.
Ventilation: All pets that are being housed in containers need some access to fresh air. A little bit of air flow goes a long way in preventing the kind of habitat that promotes the growth of mold and even small mites that live in all households, just waiting for somebody to lay a buffet down for them. Ventilation is often achieved simply by poking small holes in a container or by cutting out a section of the lid and gluing a bit of plastic or metal screen over the opening. If you do make small holes, use pins to make the holes as this will reduce the access for mites and other pests. If you use screen, it should be of a micro-screen or fine filter variety or mites will go right through. The best lids for fruit fly cultures are poly fabric lids. These provide a high amount of ventilation while preventing any access to the culture by pet bug cage pests like mites, fungus gnats or phorid flies.
Humidity: The media in your fly culture should always be in a state slightly between solid and liquid. Too wet and the adult flies get stuck in it and may drown. Too dry and the larvae can dry out or will have difficulty swimming and feeding their way through it. A little water should usually be added to the media from time to time, as it reflects a dry, too-solid appearance. In a large 32 ounce culture a teaspoon is probably the right amount. For a smaller culture, a few drops may be all that is needed. I tend to use distilled water for all the culture I make, though tap water is generally okay.
Temperature: Room temperature is just fine for raising fruit flies. However, keeping them in the range of 75 to 83 degrees will promote faster growth and reproduction. In warmer conditions, it is especially important to ensure the media doesn't dry out.
Food: Fruit flies eat the media in the bottom of the culture. Usually this is about half an inch deep, regardless of the size of the culture container. There are various recipes that you can create yourself. Most are based on potato flakes. Simple Google and Youtube searches will yield many different recipes that you can try at home. There are many pre-made mixes that can be purchased with long lists of beneficial ingredients in them. Hot water is added to this dry mix and the anti-mold properties of these mixes vs. many homemade mixes are clear.
Shipping: Fruit fly cultures are somewhat difficult to ship. The adult flies are sensitive to extreme cold and hot temperatures. Heat and cold packs are often necessary to buffer exposure. The media at the bottom has to be moist enough to support egg and larval development, but not so moist that the media will spill and make a huge mess when the shipping carriers routinely turn the boxes upside down between origin and destination. In cases where this happens and a culture shows up a little messy, the resolution is usually as simple as turning the culture upright and tapping it firmly on a counter top a few times. Larvae and eggs are not affected by the orientation of the box. They will find the media regardless of where it might move around in the container.