We use larva of the Wax Moth, or Galleria mellonella. They sell the larva in quantities of approximately 250. It is best to use them within two weeks of receipt. It is not necessary to feed or water them during storage. Cover with a lid or saran wrap with small holes for air and put sample in dark at room temperature for about a week.
Monitor insects to watch for death.
Occasionally, insects that don't die begin to pupate. See picture below for examples of dead versus alive insects. Used with permission Photo of Galleria mellonella . Larva on far right is alive, other three are dead. In this picture, you may be able to see the off-white clumps of nematodes emerging from the insect carcasses.