crawling larva A:
larval Stratiomyid (soldier fly) dipteran (family Stratiomyidae) 
It would be too tough to call what the instar is... unlike mayflies which
may have 20 or more instars, Dipterans such as the stratiomyiid have only
3-4.  They are very tiny and don't stay long within the first instar.  This
one appears to be nearly full size, so I would probably guess that it's in
its 3rd instar.
(ID and info by Peggy Wilzbach & Ken Cummins)