Author: Rob Torrens
Date: Friday, April 19 2002
These are small (about 3mm), prolific, easily reared and relished by smaller fish, particularly surface feeders. While being called wingless they are probably better described as being stump winged, as they still have wings but they are deformed so that they can’t fly.
The fly’s body is soft and floats on the surface, where it can survive for hours. The larvae can be picked out and fed directly (though this is messy and probably involves too much effort for the reward).
- Larvae, pupae and adults will live together in the one bottle.
- At room temperature the time from egg to adult fly is about 2 weeks. If the temperature is higher the development is accelerated but the higher temperature can encourage bacteria, fungi and mites.
The media for raising fruitfly varies, though two of the simplest are:
- Ripe banana with a little yeast added, leave this for 2-3 days for fermentation to start, then add the flies.
- Add 0.5-1cm of cornmeal/oatmeal (or a mix of the two – the cornmeal seemed to make the culture remain ‘sweeter’ for longer but also went runny very quickly hence the mix of corn and oat meals) to the bottom of the culturing container, pour some boiling water over the mix to get it to gel, allow to cool, then sprinkle over some yeast and sugar. After fermentation has started the flies may be added.
I put this media into the bottom of a medium sized plastic container, let it ferment for a couple of days and then introduce the fruitflies. The larva live in the media and will then crawl up the sides to pupate and then the adult flies congregate on the sides and lid.
Regarding the lid – I normally just cut a hole in the top and fill the hole with a plug of filter wool or cotton wool. Make sure that the plug is quite dense so that larva want crawl through it. This is less effort than carfeully gluing a bit of stocking over the hole. Just poking holes in the lid causes problems – though the adults may not be able to escape through small holes the larva can and end up pupating on the outside of the container.
Points to note:
- When the culture is first prepared, before adding the flies, there may be a build up of alcoholic fumes too strong for the flies. After 3-5 days this is no longer a problem.
- Cultures shouldn’t be exposed to direct sunlight.
- New cultures should be started every 3-4 weeks to assure a continuous supply.
- I keep the cultures in the hot water cupboard so that their live cycle is speed up (so far I haven’t had problems with mites, fungus etc).
- The mix will start to sour and smell after a while, this is probably a good time to start a new culture before all the adults die.
- If the mix becomes too runny but in a piece of dry bread to soak up the excess moisture (the adults seem to have a death wish and will drown themselves if the mix is too runny. Some people had in a piece of carboard going from the bottom to one of the sides to act as an escape ladder for the adults).
As these are small and remain on the surface they are ideal to feed to tetras, hatchet fish, killies and others that I can’t think of at the moment.
The way I feed them out is to open the container over the open tank, tap the lid a couple of times on the side of the tank and all of the adults that were holding onto the lid are now on the water surface. While you’re doing this your other hand (holding the container) should still be above the tank so that any escapees end up in the tank. Put the lid back on the container and proceed to evict any stray flies that may have ended up in the tank cross bracing etc.
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