Pandinus imperator. I haven't seen her in a couple of months or more. The last time I saw all of her now 3" babies (born 26 Apr 11) at the same time was early September. I think the babies recently molted again, and there are new burrows. There is another adult female and an adult male in the tank, too. Bertha is HUGE!!! I guess she could be getting ready to have more scorplings. Isn't gestation period about 6 - 7 months?
I guess it's also possible that the younger female is now Bertha-sized and gravid.

I need a bigger tank...

They will have multiple generations in the right enclosure, no problem, but does take a while for them to mature. I kept mine, which made it three generations before a heater outage, in a 40 breeder. They're quite awesome to watch.

My whole family has had a great time watching these guys, Christian. One more than one occasion I have found my octogenarian mother on the floor in the dark with the black light peering in the scorpion tank. LOL

What is the maturation rate on them? I got an adult female (Bertha), a nearly adult male, and a juvenile female in December 2009. I don't know if Bertha has molted at all since I've had her. The male and juvie female have molted at least once, to my knowledge.

The babies popped out larger than I remembered from my imps 30+ years ago, and have continued to grow like weeds! I didn't expect them to be this big this soon.

I think a 40L would suit them much better. They are in a 20 right now.

Growth is dictated by food, temperature, and I think some humidity... I do not have an ideas really. It happens with you keep things for years and years and do not keep great notes on all 30+ in the tank. I do notice the younger ones are more grey than black. I attribute this to rapid growth and missing elements in the diet, but it's only a guess. I did not see any problems in the third generation though.

Your third generation was a little more 'sociable' (visible), wasn't it? Once my babies got >2", they have stayed burrowed more, like the adults. Hard to keep accurate records when you only see them periodically. :-)

I've had trouble keeping temp and humidity up to recommended numbers. Temp averages 80ish and humidity about 65.

I never messed with them, so I never noticed a different in visibility. They were out prowling regardless, if I forgot to feed them. I will say all of them stuck to the burrows if they were not hungry!