Semi-defined Medium
Updated July 17, 2015
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This rich medium was described by Backhaus et al. (1984). Although expensive, flies are much more productive on this medium compared to cornmeal-molasses-yeast food (at least 10x more productive in our hands) and it pumps extremely well. The recipe below makes 1 liter and can be easily cooked in a microwave oven. Nutri-Fly™ "German Food" Sick Fly Formulation (Genesee Scientific) is a pre-mixed version of this recipe.
The recipe
Agar 10 grams
Brewer's Yeast 80 grams
Yeast Extract 20 grams
Peptone 20 grams
Sucrose 30 grams
Glucose 60 grams
MgSO4 x 6H2O 0.5 gram
CaCl2 x 2H2O 0.5 gram
Propionic acid 6 milliliters
10% p-Hydroxy-benzoic acid methyl ester in 95% ethanol 10 milliliters
Distilled water add to above to make 1 liter
*adjust agar concentration according to the gel strength of your agar
Cooking instructions
  1. Stir, one at a time, each ingredient except propionic acid and p-hydroxy-benzoic acid methyl ester into most of the water. Add additional water to bring the total to 1 liter.
  2. Bring mixture to a boil and turn off heat source.
  3. Cool to 60oC.
  4. Add p-hydroxy-benzoic acid methyl ester, stirring constantly.
  5. Add propionic acid just before dispensing.
  6. Dispense when the temperature of the mixture is between 40o and 60oC. The medium will separate if it is too hot when poured.
  7. Store at 8oC until ready to use.