Crush the dill seed, mustard, and cumin in a spice grinder or with a mortar and pestle. Pour the spices into a 5 gallon stockpot along with the chili powder, paprika, red pepper flakes, rosemary, thyme, dill, sage, and parsley. Fill the pot 3/4 full with water, and bring to a rolling boil over an intense flame.

Add the blue crabs, cover the pot, and boil until all of the shells turn red, and the meat is no longer translucent, about 20 minutes. Stir the crabs occasionally as they boil to ensure even cooking.