John Skillcorn
Costa Rica
Last updated: 17 August, 2002
For the majority of the Drosophila species likely to be encountered, the standard banana and Ready Brek mixture will probably suffice. However, for the purists among us, and for those species for which the simple medium won't work, here are two recipes from Prof. Shorrocks' book:
Standard Medium
Ingredients
| cornmeal (maize meal) | 13.5g |
| molasses | 18.0g |
| agar | 2.0g |
| Nipagin (mould inhibitor) | 0.3g |
| water | 100cm3 |
| This quantity is enough for four small milk
bottles. 1. Pour two-thirds of the water into a pan. 2. Add the cornmeal and molasses to the cold water. 3. Bring the mixture to the boil and cook for several minutes. 4. Add the agar (and Nipagin if using) to the remaining cold water and mix them thoroughly. 5. When cornmeal and agar are ready, pour in the agar and cook the whole for a few minutes longer, stirring constantly. The mixture is ready for use while it is still thin enough to pour easily, but will gel firmly on cooling. |
Note: all ingredients should be mixed in the cold water first to prevent lumps forming, and the food should be stirred constantly.
The day before flies are to be put into the containers, a generous sprinkling of yeast granules should be placed onto the surface of the set gel. However, Prof. Shorrocks recommends the use of fresh yeast (obtainable from bakeries in small amounts.)
Fungus-feeder medium
Ingredients:
|
porridge oats |
5.0g |
|
brown sugar |
5.0g |
|
dried yeast |
12.0 |
|
agar |
3.0g |
|
Nipagin |
0.3g |
|
water |
100cm3 |
This medium was developed by Prof. Shorrocks, and has been found to be especially effective when trying to culture those species of Drosophila which use fungi as the food source.
1.
Mix the cereal, brown sugar and dried yeast with about two thirds
of the cold
water in a pan.
2. Add the agar and Nipagin to
the remaining cold water.
3. Bring the mixture in the pan
to the boil and cook for just a few minutes
until the yeast has been killed.
4. Once the agar and mould
inhibitor have been added, the whole should
be cooked for about one minute,
after which the medium will gel
firmly on cooling yet pour easily while hot.
Note: no yeast granules need be added to the culture bottles before the adult flies are introduced.