Fruit Fly Culture Calendar
Two species, two clocks. Hydei runs about a week behind melanogaster at every stage.
| Stage | Melanogaster | Hydei | What you see, what to do |
|---|---|---|---|
| Start | Day 0 | Day 0 | Adults on the excelsior and walls, media wet and uniform. Label the cup with the date. |
| Egg laying | Days 1–4 | About a week behind | Activity peaks. You can feed from these flies, but go easy: you want them laying. |
| Larvae | Days 5–10 | Days 8–12 | Media looks churned. White grubs near the top. The adults die off. Normal. |
| Pupation | Days 11–13 | About a week behind | Brown pupal cases on the walls and excelsior. The cup looks dead. It is not. |
| First new flies, peak harvest | Days 14–20 | Days 19–25 | New adults by the hundreds. Harvest in the morning before the cup warms up. |
| Start the next culture | Day 14–17 | At its peak | Split 40–100 adults into fresh media (hydei at the top of that range), or order a new culture. Either way, a fresh culture every 2–3 weeks. |
| Second harvest | Days 21–27 | About a week behind | The new generation lays its own eggs. A partial third wave is possible; yields drop. |
| Exhausted | Day 30–35 | Past day 40 | Media spent, production tails off. Bin it when it stops producing, not on a date. |
| Retire before mites | 4–5 weeks | About 6 weeks | Mites move in on spent media. Seal the cup in a bag and freeze it 24 hours before the trash. |
Keep it going
- Temperature 70–80°F. Production slows below about 65°F and stops near 60°F. Above 80°F speeds mites and contamination, and some flightless flies grow working wings.
- Indirect light. No direct sun, no fridge top, no garage, no heating vent.
- Hands off. No misting, no feeding, open only to harvest. Look once a day. Upright, vent lid unblocked.
- Dry, cracked media on a cup under three weeks old: trickle about a teaspoon of dechlorinated or distilled water down the inside wall. Never soggy. Past four weeks, dry media means the cup is spent.
- Splitting: clean 32 oz vented cup, fresh media about 3/4 inch deep, a pinch of baker's yeast, excelsior, 40–100 adults. Do not disturb for 5 days. Producing in about two weeks.
- Mites: new cups (or boil reused ones), media stored dry and sealed, a shelf away from any grain product, spent cups retired on time.
Troubleshooting
- No new flies. In order: too cold, too few starter flies (under about 25 is a gamble), bad media (dry, cracked or moldy by day 5), opened too often.
- Tiny brown specks crawling. Grain mites. On a spent cup, retire it. On a young cup, move 15–20 clean adults to fresh media and bin the original.
- White mold. Light fuzz on fresh media burns off. Spreading mold means media too wet or no inhibitor: start over.
- Sour, ammonia or rotting smell. Contamination. Move 15–20 surviving adults to a clean cup.
- Flies flying. Too warm. Move the cup somewhere cooler; the next generation goes back to normal.
- Escapes. Harvest cool, lid ready, and a dish of apple cider vinegar in the room.