They have to be kept in an incubator to reproduce faster. They take about two months when kept warm. they must have a supply of water, potato, cucumber,etc. and bran or whole wheat flour. I don't really know how to gut load them.
The Darkling Beetle [aka the mealworm] will lay eggs in the bedding that shouldn't be removed then hatch into a larval state which starts out small but eventually increases to a large larva that is finally ready for pupation to later hatch and become a Darkling beetle.
http://insected.arizona.edu/mealrear.htm
"Life history parameter Typical Value Range References:
Time spent as surviving egg: 10 to 12 days (Hill 2002).
Time spent as surviving larva: 12 to 54 days.
Time spent as surviving pupa: 20 days (not available, Hill 2002)
Time spent as surviving adult: 80 days (60 to 90 days, Hill 2002)
Number of eggs per surviving adult: 80. (0 to 500 days, 1937, Hill 2002, Greenberg and Ar 1996, Hill" Wikipedia