Drosophila - the last word

a	Some plastic drinks cups - numbers will vary according to how many cultures you want to set up. Half pint containers are ok, made of transparent plastic. These must be newly bought. DO NOT RECYCLE these items.
b	One clean, pint-sized plastic cup, again newly bought.
c	A roll of paper kitchen towel.

d	Some newly bought elastic bands of a size that will easily fit round the mouth of the plastic cups without stretching to their limit too much. DO NOT RECYCLE these items.
e	A pair of kitchen scissors.
f	Some ripe bananas, the riper the better.
g	Some yeast granules, either in a re-sealable tin or in foil sachets. In UK, 'Allinson traditional dried active yeast' is a reliable make.
h	A 'clean' (check carefully as this vitally is important) culture of fruit flies, either small, brown D. melanogaster or large, black D. hydei.
i	A large glass or nylon bowl, potato masher and dessert spoon.
j	Spray bottle of disinfectant surface cleaner and sponge.

a	Wash your hands. Using the large bowl and the potato masher, mash the ripe banana to a pulp. Some people mix in an equal volume of ReadyBrek (in the UK this is a sort of oat-based instant porridge which, when dry, has a flaky appearance) but this is not important. It simply has a drying effect and helps stop the medium becoming too watery, so it will be much more 'stodgy' if used. It has no food value as such.
b	With the dessert spoon, put about an inch (two and a half centimetres) of mashed banana in the bottom of each plastic drinks cup. Try not to touch the side of the cup (but it doesn't really matter if you do, but KEEP IT OFF THE EDGES OF THE MOUTH OF EACH CUP).
c	Sprinkle a good helping of yeast granules onto the surface of the mashed banana in each cup. THIS YEAST IS ESSENTIAL. Your cultures will die out if you do not supply the yeast, as this is what the larvae feed on. The actively growing yeast also helps to prevent mould developing.
d	Take half a sheet of kitchen towel, screw it up tightly into a small ball and place a ball in each cup on top of the mashed banana. This forms a temporary 'perch' for the fruit flies.
e	Take full sheets of kitchen towel and fix them over the mouth of each cup with an elastic band, one sheet per cup. Trim off the excess paper towel leaving a 'frill' of about an inch all the way round the mouth of the cup.
f	Clear a whole section of work-top in your kitchen and clean the surface with a disinfectant cleaner and sponge.
g	Put all your prepared cups onto this disinfected work top and remove all the paper towel covers. Put them safely onto a clean section of work top where they are easily and quickly accessible to you.
h	Wash your hands. Take your 'clean' culture of fruit flies and, partly removing the top of the container, sprinkle a couple of dozen fruit flies into the empty, dry, pint size plastic cup. RECLOSE your culture.
i	Keeping the flies in the plastic cup by periodically tapping the base on the work top, sprinkle a dozen or so fruit flies into your first prepared cup containing banana, yeast and paper ball.
j	Put your pint cup down and quickly place a paper cover over the mouth of the culture vessel you have just seeded with fruit flies. Secure it with an elastic band.
k	Pick up your pint cup again (refill with flies as necessary) and sprinkle a few more fruit flies into the second of your culture cups. Repeat this process, cup by cup.
l	You are finished when all your cups containing banana and yeast are sealed with paper towel, and each has a starter colony of flies inside.
m	If you have already tried and failed, then find a new culture area as far away from the old (contaminated) one as possible.
n	Keep these cultures in a warm (twenty-four degrees C, seventy-five degrees F), clean, mite-free area (ten days for D. melanogaster; twenty-three days for the larger, black D. hydei). Do not worry if your cultures seem to be generating a lot of water and carbon dioxide gas. This is quite normal and will not affect the developing culture. The water will eventually dry off after a week or so.
o	Check each culture periodically to make certain that there are larvae present on or at the surface of the culture medium. You will see in particular their black mouthparts actively moving as they feed on the yeast.
p	When cultures start to produce their first crop of flies, set up new cultures as instructed above (but pay attention to special instructions concerning D. hydei about this - see the BDG Website). Be careful when extracting flies from these fresh cultures as the culture medium might still be a bit 'sloppy', especially if still warm. The mature cultures can be kept at a lower temperature now in order to slow down their development while the new ones can be incubated at the higher temperature.
q	Each time you remove a culture for feeding purposes, make certain that it does not come into contact with any surface where mites have been known to exist. If it does happen that you suspect they have come into contact with such a 'suspect surface', then DO NOT return that culture to the incubation area. Keep it separate but by all means use it as a feeder culture until it naturally dies out. However, each time you use this contaminated culture, WASH YOUR HANDS afterwards before you touch any clean culture.
r	Once cultures come to the end of their useful life, dispose of them IN THE DUSTBIN in their entirety. Do not leave them, or any part of them, lying around to collect dust and mites.