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a family of insects of the order Megaloptera. They are slow-moving, dark-colored insects. They have two pairs of membranous wings (20 to 40 mm in spread), which at rest assume a rooflike position covering the abdomen. There are about 30 species. Sialidae live near water. In the USSR, the Sialis lutaria is widely distributed. The insects of this species attain a length of up to 12 mm and have black wings. The first flight of the adult insects occurs in spring or at the beginning of summer. Eggs are laid on the leaves of reeds and of other water plants. As the larvae leave the eggs, they fall into the water. They live on the silty and sandy bottoms of lakes, ponds, and reservoirs. In some places they are found in masses and serve as food for fish. They leave the water in order to pupate.