This is the second day I've found similar masses of diptera (?) larvae streaming forward, almost like a single organism, across a brick walk. Each group observed had at least one larger maggot among them. It rained last night and this photo was taken in the morning. Looking at individuals under a dissecting scope I could not see any hooks, hairs or extensions around the mouth (excluding the larger white maggots which did appear to have hooks extending from the mouth). The specimens had no legs.