I used to get a lot of 'runty' moths but I think I've figured it out. Once I stopped moving the cocoons, the moths hatched out perfectly formed. The cocoons are attached to a surface and should stay there, no moving or changing orientation. In the wild the cocoon would stay put where it was attached, so that makes sense. I'm guessing the pupa is fragile and can get damaged easily if flipped around? It also seems more deformed ones hatch in winter, making me think the lower humidity affects them. Since I've started keeping the container covered with paper towel and adding a moist cotton ball for humidity, that problem has almost disappeared.
When I notice some of the full grown worms starting to leave the pack and not eat, I put them into sections of paper towel tube (or toilet paper tube) cut to about 3", slightly flattened. The rolls are kept in a lizard ranch type kritter keeper. Stuff a worm in and let him get down to business. Sometimes they wander around looking for a different tube but eventually they do start spinning. I've even had two share a tube, no problems. Depending on the ambient temperature, it can take as little as 2 weeks for the moths to emerge but it has taken as long as 6 weeks.
Moths only live to mate, this CB strain was bred for silk production at the expense of flying ability, they try like crazy to fly but can't. One a pair starts mating, it can take a day or longer for them to finish, they're oblivious to anything else. I move the pair to a delicup where they stay until done, the female lays her eggs in there. If the male still shows signs of life and I need another one, I'll try to pair him up with a female though I find that the fertility rate of those eggs isn't as good. Usually I don't mate him twice if I can help it. Once the moths are done their respective jobs they get fed to the leos as treats. I do find there are more females than males but not too big a discrepancy, usually 2:1.
There's a PDF file online someplace about the problems with silkworm raising as related to the silk industry. It mentions the translucent cocoons as being a problem with diet. I've noticed more translucent ones in winter when I can only feed the chow, the summer worms get mostly real mulberry leaves and there are hardly any translucent cocoons. If I can find the file again, I'll post a link for anyone who wants to read it. That same file has a recipe for making your own chow but it sounds like a pain. It's also geared to silk production, not worms as food so I'm not going to try the recipe myself, some of those ingredients don't sound healthy for a leo even though they might not kill the silkworm itself.
It might not be an 'official' sexing method, but I find the females have a more intricate pattern on their wings. You can see it fairly well in the picture above. Male wings are fairly simple, females have a few extra 'lines' crossing the wings.
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