culture medium for fruit flies

[Matthew]

Does anyone have any recommendations for culture medium for fruit flies?

Thanks

[Rob]

The culture medium I ended up using was a porridge mix made of roughly 60% rolled oats and 40% cornmeal. When I used only cornmeal the medium liquified too quickly but didn't smell as bad as old cultures based only on rolled oats (that's why I now add some cornmeal to the mix). I prepare it like a porridge (not salt or milk though - just water) - you want that heat to get the mix to gel. Once it's cooled sprinkle over some bakers yeast, a little sugar and give a light misting of water.

I found that fruitfly all have a morbid facination for water droplets (normally investigated by putting their head in them and drowning) - so perhaps wipe the sides to remove the drops or bang the container so the drops run to the bottom.

The only problems I had with mould growth was when the initial medium was too dry.

If the medium in the container is getting a little runny (but still smells ok'ish) then you can put in a piece of dry bread to soak up some of the liquid and act as a life raft for the flies.

I had problems with the lid of my culture initially - just did the standard thing of stabbing holes in the plastic - the adult flies couldn't get out but the maggots (which climb the sides when it's time to pupate) climbed through the holes and pupated on the outside of the container. So now when I set up a culture the lid has a whole about the size of a 10c piece in the middle that I put a reasonably tightly wadded piece of filter floss or cotton wool in - I've also seen people glue a piece of stocking over the hole.

Harvesting can be a little problematic in that, while they can't fly, stump winged/wingless fruitfly are still quite good at jumping. The way I ended up doing it was opening the container over the open tank shaking the flies into the tank and then spend the next 10 minutes rounding up any escapees.

[Interfecus]

My method is incredibly simple. Get a plastic bottle (one of the smaller ones, 750mL or something) or a jar and put some rolled oats in the bottom to make a layer a couple of centimetres deep. Bring the kettle almost to the boil. Pour in just enough water, stirring often, to make a thick porridge. Sprinkle a pinch of yeast on the surface, add another thin layer of rolled oats (about 5mm) to make a semi-dry layer, let it cool a bit, then add the flies. With the dry rolled oats on the top the flies will be protected from any water released as the medium cools. By the time the culture is ready for harvest the maggots will have made the dry layer wet enough to prevent it from being dislodged if you turn the culture almost completely upside down over a tank and tap it.

[Interfecus]

For a bottle a reasonably long bamboo skewer is the best thing for stirring the medium.