#2
These are puparia (the last larval skin, in which the pupa forms). The adult fly, when it emerges, inflates a sac on its head and pushes off a cap at one end of the puparium. The internal black bits you can see in the right hand puparium are the larval mouthparts. You should be able to rear the flies from these (if they're not empty!) - keep them damp, but well-ventilated, and the adults should emerge. Retain the puparium, especially the cap which may have the larval mouthparts attached, and stick them on a piece of card under the adult specimen. You do need to keep the adult alive for several days for it to mature before killing it. Good luck!