To prepare the soft-shell crabs: Put the flour in a pie dish or plate and season with a fair amount of salt and pepper. Dredge the crabs in the seasoned flour to coat, shaking off the excess. Heat the oil in a large skillet over medium-high flame. Lay the crabs in the hot oil in a single layer without crowding; you may have to fry them in batches. Be careful, the crabs have a tendency to pop and spatter. Cook the crabs for about 3 minutes on each side, turning once, until golden brown. Drain on paper towels and cover to keep warm.
Lower the heat to medium and add the butter to the pan. Let the butter melt and cook until it just begins to brown. Add the capers and wine; cook, stirring, for 2 minutes until almost dry. Add the lemon juice and parsley; season with salt and pepper. Pour the caper brown butter sauce over the crabs and serve with lemon wedges.