If I recall, its the females that are larger , the males appear to be normal sized. I thought the same thing when I started with them. My small colony I started around 6 months ago, I regularly think they are all dead, then they keep showing up. Not a comfort roach. At least not yet. Several times had a spastic one hyperspeed out of the jar, jump into a lid, run up my arm, jump again, catch it, lose again, @#$$%, catch, and throw back in , whew! stressful.