The eastern dobsonfly, Corydalus cornutus, is a large insect in the Corydalidae family. It is found in eastern North America in regions with fast-flowing streams where its aquatic larvae develop. These are known as hellgrammites and are among the top invertebrate predators in the streams in which they live. They are used by anglers as bait. Distribution The eastern dobsonfly is found in most of eastern North America. It is usually found near the swift flowing, unpolluted streams in which its larvae develop. Common names The origin of the word "dobsonfly" is unclear. John Henry Comstock used the term in reference to this species in his 1897 book Insect Life, but did not explain it. He also mentioned that anglers use the word "hellgrammite" for the aquatic larvae they used as bait, but the origin of this term is also unknown. These common names are still widely used for this and other species of corydalids, and essentially all that is known is that the earliest recorded uses appear to originate in the southern Appalachian region of the US (Kentucky, Tennessee, Virginia, West Virginia), where there were other archaic regional names and variants such as "helgamite", "hojack", "go-devil", and "grampus" (or "crampuss"), all with no definitive source or etymology. The latter name, "grampus", was used in the same region for a large aquatic salamander, the hellbender, that lives in the same habitat. Description The eggs are grey and cylindrical, about 1.4 millimetres long and 0.5 millimetres wide. They are laid in groups of about 1,000, stacked in three layers. The pile of eggs is protected by a clear fluid which dries white and is applied by the female with the tip of her abdomen. The egg mass is said to look rather like a bird dropping. The larvae are light brown with a covering of tiny dark brown microspines. The thorax has three pairs of legs and each segment is covered by a tough, dark-coloured dorsal plate. The first eight abdominal segments have lateral tactile filaments and the first seven have tracheal gills in tufts. The larvae also have spiracles allowing them to breathe on land as well as in the water. At the tip of the abdomen there are two prolegs, each with a dorsal filament and a pair of terminal hooks which enables the larva to anchor itself in fast-flowing water. The mandibles are sclerotised and powerful. The pupae