Fruit Fly Culture Lid Guide: 32 oz Deli Cups

Bought a fruit fly culture from the pet shop? Many come in a 32 oz deli cup with a basic press-on lid. Swap that lid for the Fruit Fly Culture Lid and you get a vented lid with a threaded spout, so you can shake out just the flies you need instead of peeling the lid off and hoping nothing escapes. No mixing media, no new cup.

First, Check Your Cup

Pre-made cultures don't all use the same cup, and cups that look identical can differ slightly at the rim. Before you buy, measure across the top of your culture cup, from outside edge to outside edge. If it measures 4-9/16" (4.6"), this lid fits. Fabri-Kal and Karat 32 oz deli cups are this size.

Measure across the top of the deli cup, outside edge to outside edge. 4-9/16 inches (4.6 inches) fits this lid.

Upgrade a Store-Bought Culture in a Minute

  1. Knock the flies down. Tap the cup firmly on a table a few times so the flies drop to the bottom.
  2. Swap the lid. Quickly pop off the original lid and snap on the Fruit Fly Culture Lid, with the Vented Cap installed. Press around the edge until it's seated all the way around.
  3. Keep it going. Store the culture at room temperature, out of direct sun. It keeps producing just like before.
  4. Feed. Tap the cup again, then unscrew the Vented Cap (or the Nozzle Tip, if you're using the Feeder Nozzle) and tilt the cup to dispense flies.

When the culture is spent, freeze it overnight, pop the lid off, and wash it. It's ready for your next store-bought culture, or one you start yourself.

Fruit Fly Culture Lid on a 32 oz deli cup, shown with the Feeder Nozzle or the Vented Cap installed

Two Toppers, One Spout

  • Vented Cap: keep this on while a culture is building up. It closes the spout while letting the cup breathe.
  • Feeder Nozzle: screw this in when the culture is producing and you're ready to feed. The narrow tip lets you dispense flies directly into smaller enclosures. The small Nozzle Tip screws onto the end to close it.

Every lid includes the Vented Cap. The Feeder Nozzle is included when you choose the feeder nozzle option, and is also sold separately as a Feeder Nozzle Attachment.

The Parts

Exploded view of the Fruit Fly Culture Lid: Nozzle Tip, Feeder Nozzle, Vented Cap, Lock Ring, Vented Lid, and Spout above a 32 oz deli cup with a 4.6 inch rim

The spout inserts from underneath the lid and the Lock Ring threads onto it from the top. The Vented Cap and Feeder Nozzle share the same threads, so either one screws into the top of the spout. The lid snaps onto the rim of the cup.

Lining Up the Spout Key

A small triangular key on the underside of the lid fits a matching notch in the spout's flange, so the spout can't spin when you tighten or loosen a topper.

  1. Push the spout up through the lid from underneath, turning it until the notch drops over the key and the flange sits flat.
  2. Thread the Lock Ring onto the spout clockwise and tighten it until it's snug.

The triangular key under the lid lines up with the notch in the spout flange; then the lock ring is tightened clockwise

Starting Your Own Culture (Optional)

Want to make your own cultures instead of buying them? The lid works just as well on a fresh cup.

  1. Mix your fruit fly media in the bottom of a clean 32 oz deli cup. For Repashy Superfly, use 3 tablespoons of powder and 2/3 cup boiling water.
  2. Fluff a handful of excelsior (wood wool) and add it on top of the media. This gives flies and larvae something to climb and pupate on. Perforated paper or a folded coffee filter also works.
  3. Let the media cool completely to room temperature. Warm media will kill your flies.
  4. Add 15–30 flies from a healthy culture, then snap the lid on with the Vented Cap installed.
  5. Store at room temperature, out of direct sunlight. Expect larvae in 5–15 days and new flies in 10–30 days.
  6. When flies are ready, swap the Vented Cap for the Feeder Nozzle, unscrew the Nozzle Tip, and tilt the cup to dispense. Screw the tip back on when you're done.

Tip: Put the lid on a clean, empty deli cup to dust flies, crickets, or worms with supplement powder, then dispense them cleanly through the spout.

For species, media recipes, rotation schedules, and troubleshooting, see our full Creating Fruit Fly Cultures guide.

Will It Fit My Cups?

The lid is made for 32 oz deli cups with a 4.6" (4-9/16") top diameter, including Fabri-Kal and Karat. Many pet shop cultures come in cups this size, but not all of them. Even 1/16" difference at the rim can keep the lid from snapping on securely. If your cup measures differently (see First, Check Your Cup), use flies from it to start a fresh culture in one of our Fabri-Kal 32 oz deli containers.

Care and Cleaning

Parts are 3D printed in PETG. Hand wash with warm water and soap, or a water and vinegar solution. Do not put plastic parts in the dishwasher. To clean thoroughly, unscrew the Lock Ring to separate the spout from the lid. When you reassemble, seat the spout's notch on the key and tighten the Lock Ring snugly. Colors of printed parts vary.

Shop the Fruit Fly Culture Lid · Prefer glass? See the Fruit Fly Culture Jar Guide.

Designed and 3D printed in St. Louis, MO.