These are evidently the puparia of the large, leggy flies that kept eclosing inside my Osmo*derma emeri*cola rearing container. I say evidently because, although I didn't see a fly exit any of these puparia, they are the only puparia I noticed while pawing and sifting through the rearing container, they are the right size for these large flies, and there were about the same number of these flies that eclosed inside the container.