I broke open one of the dried yucca stalks to see if any of these moths were still in pupa stage, I found several empty brown coccoon sacs and one that was apparently occupied. I removed it and was searching for more when I noticed something had wiggled its way out of the sac, gyrating its abdomen just like many beet*le pupae do.

Under magnification I would say this is the intermediate stage between the larvae in my yucca stalks and the five (at latest count) small white Yucca Moths in my bathroom window. I've therefore linked all the images, making another moth development sequence for bugguide. Lacking is the larva before building its sac.