The narcissus bulb fly is one of my most despised pests. Besides attacking vacationing Hippeastrum it will also infest narcissus, galanthus, lycoris, and leucojum bulbs and I would keep an eye on these as well since they are probably also under attack and are likely the source of your infestation. Daffodils and snowdrops here will fade away in a year or two if left untreated. I really hate these things.