I found several dried yucca flower stalks that showed evidence of birds pecking into them for insects. I broke them off close to the base, then broke them open to look for grubs, hoping for beetle larvae and already wondering if these were host-plant-specific beetles brought into the area with these yuccas, if they came later, or were they of a species that was already here and took a liking to yucca stalks?
I guess I was a little disappointed to find what appear to me to be hymenopteran larvae, although the same set of questions could certainly be raised about them. They appeared to be pupating -- or getting ready to pupate -- inside their little brown sacs. I associate these sacs with hymenopterans, having had some wood wasps emerge from some in my early days of collecting and rearing larvae. Also, their lime-green hue makes me think they are hymenopterans rather than beetles. I've found other colorful wasp larvae
that pupated and emerged, but colorful beetle larvae are not all that common.
I saved a few stalk sections that might or might not contain more grubs. Those I extricated for photos became live food for various adult beetles. I doubted they would have survived. On trying to completely remove a grub for a photo I found that their skin is attached to their sacs.