Known in the US as the "Indian meal moth", it is the most widely distributed, and problematic, stored product pest in the world. Sunflower seeds are always a good source. Any number of nut, seed, grain, milled grain products may be infested. You can often see them flying about in the pet food isles of some stores, feed stores, et cetera. Put the sunflower seeds in a freezer for 4-7 days and that should do it for the bag. Smack the moths that fly about that may be in your house. You may be able to purchase a pheromone trap for your house if there were very many. I suspect the bag had a lot of "webbing" in it. Larvae will be smallish, often creamy to light green in color. Ah, the joys of global trade. Best of luck!
