I think I know 1 reason why alot of l1s of any species tend to die off as some get blockages at their back ends of fecal matter and so they cant get rid of it. I think it just keeps mounting till the mantis is unable to function and dies but thats just a observation of mine and its hard to clean a l1 of this problem with a sprayer of course.Some other ways a l1 can die of course being squished or eaten by another sibling or another insect or if the temp is too high and maybe humidity but just gives a idea of some ways a l1 would die in case anyone wonders!