From my experience (the little bit I have), oranges are basically Roach Viagra...I put a few slices in when I got them last weekend on Friday, and by Monday, I had a fresh batch of babies. They were probably pregnant already, but I had all adults 1 day, then a few later, a bunch of babies showed up.
My tip, orange slices and a heating pad under a good portion of the cage, also make sure they have plenty of ventilation and places to climb (I did this by going to my local Denny's and asking for a stack of egg flats, just put a few in your tub vertically and you are good). Also make sure you use a tub that is not see through, or keep them in a dark place if that is all you have. They hate light and run from it when it comes on.
I hope this helps!
