I want to know because in my small colony of dubias i only have one female so far and the rest of the adults are males and i have some nymphs.
I'm getting some more dubias soon to increase the colony size

I'm pretty sure that the last segment on the abdomen will be smaller in males and larger in females, but to see it on those leetle guys you'd probably need a microscope, or REALLY good eyes.

thanks, my nymphs are quite big and I can see the last segment pretty easily most of my roaches are male hope fully I will have more females with my other roaches I ordered