How to tell if your scorpion is close to molt ?

[Redjunior]

I am asking cause I haven't been able to tell when my scorpions are getting ready to molt, and unfortunately I lost a deathstalker to crickets. I put some in with him during a usual feed ( every 10-14 days ) left them in there while I slept ( about 6 hours ) I woke up and upon checking on him, I discovered he went into a molt and got eaten. Being infuriated, I figure this is the best place to ask, since my research isn't telling me much.

Thanks in advance for info !