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care sheet, drosophila melanogaster, fruitfly -

Care Sheet: Flightless Fruit Fly (drosophila melanogaster)

Common name: Vinegar fly, fruit fly.
Scientific name: Drosophila melanogaster
Size: 2.5mm long
Lifespan: 21 days approx
Diet: Detritivore; decaying fruit and vegetable matter.
Appearance: Tiny flies with red eyes. Varieties from labs and within the hobby exist with vestigial wings, making the flies flightless.
Use in hobby: Feeder insect for small fish, birds, frogs and invertebrates.

Housing


Our recommended size: 425ml cup or jar with a vented/filtered tight fitting lid. Any ventilation should be filtered with something like a filter paper, cloth or fine mesh. If you're able to make tiny pin holes, no filter is needed.

Temperature: Keep out of direct sunlight. Avoid above 28C for extended periods, flies may genetically revert to flying form in future generations. Keep at 20-24C for the fastest possible breeding.

Substrate: 2cm thick layer of a fruit fly food mix. You can buy premade lab mixes, use our recipe or use your own recipe from online. Fruit fly larvae feed and grow in the substrate.

Decor: Excelsior (wood wool), folded coffee filters or shredded paper for adult flies to grip onto. Excelsior works best as it does not sag over time. Not a lot is needed. Often cultures are shipped over-packed for safety in shipping. 

Maintenance: Once a colony has started, little maintenance is needed. A fruit fly culture lasts about 1 month before depleting. To continue maintaining fruit flies for your animals to eat, start up and keep multiple cultures when your original cultures are producing flies at their peak.

  • Place in the food substrate into the container first. Add fresh new wood wool or shredded paper before shaking in about 50-100 adult flies to start the culture. It takes several days for larvae to appear, read on below for more detail on reproduction.
  • Clean out any old culture cups instead of throwing them away. If cups are broken, try to recycle them. Jars can be used for a more permanent solution.
  • Scoop out and trash/compost the contents of the cup. Soak and wash with soap, air dry before reusing.

Notes on mold: Mold seems to occur in home made recipe cultures for a variety of environmental reasons. We're experimenting with ingredients to make this occur less often, but for those who keep getting mold- lab grade mixes work best.

Maintaining warmer temperatures can also help fight against mold. The yeast the grows in the food substrate does better with warmth and can out-compete the mold! 

Feeding

The main point of raising fruit flies is to feed them to small animals. Harvest the flies when they start emerging from their pupae.
  1. To harvest, tap the upright culture cup on the table liberally to dislodge flies from the top and sides to avoid escapees. 
  2. Remove the lid quickly, keep tapping the cup if the flies try to climb up.
  3. Angle and tap the cap directly over the enclosure of the animal you wish to feed, and the flies will fall in. 
  4. Re-apply the lid as soon as possible to avoid escapees and contamination from wild, flying fruit flies. 

Behaviour and Biology

There are several species of fruit fly in the world. Drosophila melanogaster is a very common species. For many people, these flies are seen as a pest around sweet foods and fruits. They generally are only a pest in the presence of rotting food. 

In captivity, drosophila melanogaster is commonly used for studies in labs due to their short lifespan, ease of breeding and genetic selection. Due to this, vestigial wing (small reduced wing) varieties exist. This has made it easier to handle these flies, both for scientists and hobbyists!

Reproduction

Sexing drosophila melanogaster is normally not needed when breeding, as cultures are started with 50-100 flies usually. It is quite easy to tell apart males and females, as they are sexually dimorphic. Males have shorter abdomens and have a distinct black patch on the end of the abdomen.

The reproduction of drosophila melanogaster is well studied, their sexual preferences and biological development are extremely detailed in knowledge, but we will cover only the basics we need to know as hobbyists.

Handy Tip: Label the date of when a culture was started on the container. This will help you keep track of multiple colonies and how they are doing!

  1. The life cycle of a single fly usually plays out for about 21 days, from egg to death. In warmer temperatures this may be faster, and in cooler temperatures much slower. In winter, you may need to heat your cultures.

  2. The female fly can lay up to 100 eggs a day, and will do so into the nutrient rich substrate.

  3. After 12 hours or so, the eggs hatch into tiny larvae and feed on the substrate, burrowing through it.

  4. Overtime the larvae grow larger and larger, usually between 7-10 days.

  5. Mature larvae leave the substrate, climbing into surfaces to pupate. In a culture, they can be seen in the sides of the cup as rice-like pupa. 

  6. After 4-7 days, adult flies emerge from the pupae and a noticeable population spike occurs.

  7. Adult flies generally die within 7 days, so it is highly encouraged to start new cultures once a culture starts to produce flies. The old substrate cannot be reused, as it has either been depleted or is no longer suitable for new larvae to grow in.

What happens if my vestigial wing flies have started to develop flying wings?

If your cultures have started to develop full wings and flying, it may indicate one of two things:

  • The temperature of the culture has reached 28C+ at some point, increasing chances of genetic change back to flying form. Keep cultures in a cooler room, and air condition when necessary.
  • Wild fruit flies have gotten into the culture due to it being near a wild source of flies eg. if kept in the same room as some old fruit, or near a window. 

Once a culture has been contaminated by fully winged fruit flies, it is best to discard the culture, find out and eliminate the cause, and then purchase a new flightless culture from a reliable source. 


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