Dragonfly Nymphs are the adolescent dragonfly, just before it transforms into an adult. They are from the order 'Odonata', from the Greek word, odous, meaning tooth. They can give sharp bite with their teeth (mandibles) if held carelessly.
These nymphs are short and chunky with wing pads and internal gills. The look like something from a nightmare, they have six legs which are located near the head. Nymphs can be seen on plants, among stones, and leaf litter, most of my sightings are in ponds and on the canal.
Dragonfly Nymphs are predators and feed mostly on other insects in the water. They are known cannibals. Some of the larger species feed on small fish and tadpoles. They catch their food with a toothed lower lip (labium) that is usually folded under the head. When prey comes near, the nymph will shoot out its lower lip to grab it, faster than most prey can react. The lip is then pulled back to the waiting mouth and feeding begins.
They breath by sucking water into its abdomen to move water over its internal gills. Once it has absorbed enough oxygen, the nymph squeezes the water out rapidly so it does not have to come up for air like most pond insects. This also helps jet propel them forwards in the water.
Much of a dragonfly's life is spent in the larval stage where it moults six to 15 times. The nymph crawls out of the water and moults one last time, emerging as an adult with functional wings. Dragonflies and damselflies do not go through a pupal stage to become an adult.