Emily1220 ~ Do you know how warm it actually gets? I know they do fine at 100 degrees so I can't imagine heat would cause a reduction in size...but hey... we're still learning! That's certainly an interesting observation. Could it be because they are going back and forth on being hot then not so hot? Maybe assign one drawer to be kept at room temp and compare the pupae.
oh.... would love to see photos if you are able to do the comparison !!! I LOVE pictures!
Nate ~ Oh my goodness....10,000 and 3 drawers! Love it. You can keep thousands of beetles in a drawer....that's what I do. They really don't need a whole lot of space. 10,000 though.... geesh...I need an 'envy' smilie face.

Did you replace the bottom of the first drawer with screening? For me, I find it a lot easier to keep the beetles above another container. I take out the second drawer after a few weeks and replace it with a fresh drawer. I have been emptying it into another container and keeping them in the oven to grow out.
Even my larger single container has another container in it that I put up on used thread spools to keep the beetles separate within the same container. (pictures on my mealworm page). I actually made 2 of those elevated beetle containers in case one should get over crowded but since I'm feeding out to the chickadees right now, too many isn't gonna happen again until summer.
You could still just stick 'em all in one big bin to live and multiply willy nilly.... that would be awesome... 10,000 wormies making all those pupae morphing into all those beetles. Dang, but your farm is destined to be incredible like Amy's farm!!!
Easy would be a couple bins and forget about separating. It really boils down to how much time you want to spend taking care of it. If you want to separate go for it. I still recommend a screening top drawer so that the eggs can drop into the second or a screened container in a bigger container. I do like keeping the beetles separate for 'housekeeping' reasons.
hope some of this rambling has helped
teeheee
I have had a few small Pupa but not a whole lot. I also nave noticed some large beetles and some much smaller ones as well. Is this a normal thing? YES