Mealworms start out as eggs laid in the soil by adult darkling beetles. The beetles don’t provide any care for their young; they will eat the eggs if they get a chance. They can take three days to hatch or more than a month. A warm, humid environment will usually speed up the process. Tiny mealworms emerge from the eggs -- darkling beetles in the larval stage. The larvae spend all of their time eating and growing. The mealworm stage usually lasts about 10 weeks.