Pantry weevils are very common and the larvae are very adept at finding places to sit and develop. When and if the conditions are good, they develop into the moth which in turn lays more eggs. They may even have come home with you when you bought the seed. You may have to take more steps in ridding your kitchen of these pests. Carefully check your pantry and the rice, pasta, bean, seed or nut products. Just throw them out if you see any signs of weevil cocoons. Warm air is needed for them to produce. They will bore through the cardboard into boxes of product. So if in doubt, throw it out. Good luck. Oh, even cereals and dried fruits.