Fruit Fly Troubleshooting Guide
While fruit fly cultures are simple to make and use, many things can go wrong with a fruit fly culture. This helpful guide from Josh's Frogs will aid in solving any mysterious fruit fly ailments, and put you on the right path to proper fruit fly production. I'll list common issues with fruit fly cultures, then offer solutions to get your culture producing like they should.
1. Dead, few, or no flies in culture.
There are several potential reasons for this. If the fly cultures were shipped to you, the flies may have perished during transit due to extreme temperature or rough handling by the delivery service. With hydei fruit flies, it's normal for the adults to die off before the next generation hatches. If you made the culture yourself, insure that you added enough flies initially. Remember, it takes about 2 weeks for a melanogaster culture to start producing, and 3 weeks for hydei to begin to produce.
As long as the culture is being kept in the proper conditions (60%+ humidity, 75-82F) and larvae or pupae are visible, give the culture time and it should produce flies.
2. Small, globular tan/white bugs in culture.
These are grain mites. Grain mites are present in every fruit fly culture, as well as in every pantry. They are interested in eating fruit fly media, and do not directly harm fruit flies. Grain mites can take over a culture and outcompete the flies for resources, causing the culture to crash. Generally, this is due to not enough fruit flies being put in a culture to begin with, or the culture being kept at improper temperature/humidity.
If a culture is heavily infested, throw it out. Josh's Frogs recommends disposing of all cultures older than 4 weeks, as older cultures tend to become mite magnets.
3. Moldy or Crusty media.
The fruit fly media has dried out, due to being kept in conditions without adequate humidity, or not enough water was added when making the culture. When the media dries out, methyl paraben (the mold inhibitor we use in our media) becomes inactive, and mold can grow. A crust can form at the top of the media, trapping and suffocating fruit fly larvae underneath and stopping production.
Add chlorine free water to the culture. Keeping fruit fly culture in Rubbermaid or Sterilite plastic storage drawers can help maintain higher humidity, as well.