The dragon of the stream bank. With a wingspan reaching up to twelve centimetres and formidable-looking mandibles, the dobsonfly looks like a creature designed to intimidate. The males sport exaggerated, sickle-shaped jaws that look capable of snapping a pencil. This is mostly bluff. Their bite is weak and harmless to humans, used primarily for wrestling rivals rather than defence. The females have shorter, stronger jaws that can pinch, but they are generally docile unless handled. The true life of the dobsonfly is spent underwater. The larvae, known as toe-biters, are fierce aquatic predators. They hide under stones in fast currents, using hook-like legs to anchor themselves while waiting to ambush mayfly nymphs and other small invertebrates. They have sharp mandibles that can deliver a painful nip if you step on one, hence the name. Dobsonfly larvae breathe through paired gills along their abdomen, looking like armoured alligators with tassels. They are sensitive to pollution and require clean, well-oxygenated water. A stream with healthy dobsonfly populations is a stream in good condition. They are the premier indicator of pristine water quality in New Zealand. It can take up to three years for a larva to mature. It moults many times, growing larger with each stage, consuming hundreds of prey items. When finally ready to pupate, it crawls out of the water and finds a damp crevice under a rock or log. It spins a cocoon of silk and debris, pupates for several weeks, and emerges as an adult. The adult stage is brief and somewhat clumsy. Dobsonflies are attracted to lights at night, often crashing into porch lamps with a sound like falling twigs. They do not eat as adults, living only long enough to mate and lay eggs before dying. The males die within a week. The females live slightly longer, long enough to deposit their eggs on leaves overhanging streams. When the eggs hatch, the tiny larvae drop into the water and begin the cycle again. The dobsonfly is a spectacular example of nature's all-style-no-substance approach to adulthood. A magnificent, short-lived display following a long, brutal childhood in the rapids.