The Case of a Dragonfly Nymph

There are approximately 45 known species of dragonflies (suborder: Anisoptera) on the prairies. Dragonflies have 3 stages of evelopment: egg, nymph and adult winged dragonfly. They spend most of their life as a nymph. For instance, in Saskatchewan, dragonflies are in this stage for at least one year, sometimes 2 or more years! The dragonfly nymph plays a part in the aquatic ecosystem. In its ecological niche, it is a predator. Dragonflies feed mostly on other insects in the water. They have been known to be cannibalistic and some of the larger species will feed on small fish and tadpoles. Lucky for people, dragonfly nymphs also eat mosiquito larvae. Dragonfly nymphs are sensitive to habitat disturbance and need aquatic or riparian vegetation in the waterways where they live. Their habitat is threatened by industrial and pesticide pollutants in waterways, as well as, continuing development that elimanates wetland areas. Look for signs of nymphs along the shore. Sometimes, you will find the outer layer on the bank when you are pond-dipping. While living in the aquatic environment, nymphshave a hard shell that helps to protect them against other pond animals. However, this shell does not grow with the nymph. The nymph moults. The outer layer is shed to expose a new, larger shell. This can happen as many as 15 times before the adult dragonfly is fully developed. When the nymph developes into a dragonfly, it waits until night to crawl out of the water for the 1st time in its life. The outer skin layer dries and splits along the back. In a few hours, blood starts to move throu gh the dragonflies' veins. The wings expand and become stiff. By the time the sun rises, the dragonfly metamorphosis is complete and the gill system is replaced by a respiratory system.