I've been raising mealworms for 8 or 9 months now and have noticed my pupae getting smaller and smaller. I thought moisture might be a problem so a month or two ago I started feeding vegetables more often, every couple days. I also tried adding a sponge in an open ziploc bag to the bins to try to increase humidity. A gauge laying on the substrate shows about 80 degrees F and 60-65% humidity in the beetle bin, nearly 90 degrees F and about 55% humidity in the worm bins.
I feed a variety of produce I grow myself including carrots, potatoes, string beans, beets, yellow squash, banana peppers. Still my pupae are coming out very tiny. Since the large pupae are starting to show up less often and my larger beetles are getting pretty thin in numbers, I'm desperate to get the problem fixed. I want to maintain them organically raised, so I don't want to use chemicals on them, I was thinking about pulling out the larger beetles and larger pupae to start a new bin. I don't know if selective breeding will fix the problem. I wonder if genetic diversity is a problem, maybe the population per bin is too dense? Anyone have any suggestions?