It sounds as though your garden has lily leaf beetles. The beetle was first found in the United States in 1992 and has now spread throughout New England. Lily leaf beetles lay eggs and develop only on various species of lily, including Turk's cap lilies, tiger lilies, Easter lilies, and Asiatic and Oriental lilies. However, they may also feed on fritillaria, Solomon's seal, potato, and flowering tobacco. Adult beetles are 1-4-3-8 inch long. Larvae resemble slugs, with a swollen orange, brown, yellowish, or greenish body and a black head, and cause more damage than adults. Adult beetles overwinter in the soil or plant debris. If you have only a few lilies in your garden, handpick adults, larvae, and eggs to reduce populations. The natural insecticide neem kills larvae and repels adults. Several chemical insecticides, including carbaryl (Sevin), malathion, and imidacloprid, are effective on adults and larvae.