We used to collect eggs from plates by washing them onto a mesh and rinsing them with 70% ethanol.  This procedure is found here and might still be used if there is some reason to sterilize the eggs.  In general, use the simpler procedure described below.

We normally inoculate about 50 tubs with 120 to 150 milligrams of eggs per tub. The flies that eclose approximately 2 weeks later are distributed evenly among 3 cages. Three cages of adults will usually generate at least 200 grams of eggs over the course of 6 days. A small portion of these eggs are used to start a new population of flies whereas the majority of eggs are used to make extracts for biochemical studies.

If no one has a need for eggs, you can scale the adult population down to a single cage.  15 tubs should be adequate to sustain the population.

Prepare ahead of time 50 tubs of cornmeal (recipe).  These tubs can be stored for weeks in the cold room.  Allow the tubs to warm-up to room temperature if they were previously stored in the cold.  You will probably need one or two grape plates of eggs to inoculate these tubs.

Collecting eggs and inoculating tubs:

1. Remove a grape plate from a cage. Put a fresh grape plate with a 1 inch wide, 1/8 deep strip of yeast paste i down the middle back into the cage of adult flies. It is very important to add a new plate to the cage of adults if others intend to collect eggs. Without food, the adults die in about 24 hours.
2. With a flat ended spatula, scrape 120 to 150 milligrams of embryos from the surface of the grape plate.  Weigh the embryos on a small piece of parafilm placed on the platform of the balance.
3. Pour off excess water that may be in cornmeal tub and place the embryos in the center.  Disperse the embryos with a squirt or two of water, but keep them towards the center of the tub.
4. Sprinkle 1/4 tablespoon of dry, active yeast around the perimeter of each tub. This yeast goes by the name of "Saf" yeast - it is dry and granular. Avoid adding an excessive amount of yeast, and avoid covering the eggs with the yeast.
5. Cover the tubs with screened lids and place the tubs on the metal shelves in the fly room.  If it is necessary to stack tubs, stagger the containers so the screened area of the lid remains exposed.
6. If the grape plates do not appear dried out, scrape off the old strip of yeast, rinse with water, wrap in plastic and put back into the cold for reuse. If the plates are dry and cracked, discard them.

Transfer of adults to cages (for more information on setting up the cages, go here):
The adults will begin to eclose approximately 12 days after the eggs were placed in the tubs. Sometimes, the majority of adults will eclose in unison. When this is the case, one session of transferring adults into cages is often sufficient to set up the cages for egg collections. Unfortunately, the adults often do not eclose in unison. In this case, you should transfer adults on several days: perhaps 12, 14, and 16 days after the tubs were first inoculated. The reason for multiple transfers is that the adults become unhealthy if left in the tubs for more than a few days. You can gauge when to stop transferring adults by carefully examining the pupae on the sides of the tubs. When 70% or more of the pupae look empty, the tub can be terminated.