in Baltic Amber
Stoneflies are rare in amber. The larvae form of a stonefly are even harder to find. Here is the larval form of a stonefly, Plecoptera.
A lovely piece of Baltic amber, this one is polished on only one side and show the stonefly very well. Even so, this is not a large animal.
While fully developed larvae are occasionally found in amber, the exuviae (molt) and particularly the winged imagoes are most common. The mature larvae leave the water and often climb up nearby tree trunks to shed their last exuvia and become winged imagoes. As stoneflies develop only a low affinity for flying and usually walk rather than fly in the event of danger, in search of food or to mate, their dispersal in minimal and often limited to the immediate vicinity of their original aquatic habitat.
This particular stonelfy in Plecoptera, possibly Leutridae:Perlidae (common stonefly).
The sharp thing about this is that you will just not see these very often - either finding them or finding them for sale.
Don't forget to look at the entire piece of Baltic amber: