Males (XO) are found only rarely (0.2%) in a population of self-fertilizing hermaphrodites (XX), as a result of spontaneous X chromosome loss.
Take 5-6 NGM seeded plates, put 5-10 L4 hermaphrodites on each, and incubate for 4-6 hours at 30°C. Then, put the plates at 20°C. You should get 2-5% of males in the F1 generation.
Author: Roxane Dervey