Dragonflies

• Phylulm Arthropoda
• Class Insecta
• Order Odonata

Nymph Appearance One of the largest nymphs Only stonefly nymphs compare in size Brown or green body Wide, flattened and oval abdomen No tail Large, bulbous eyes Outspread legs Grasping lower lip rapidly extends outward

Nymph Behavior

• Don't have gills
• Tracheal system works by diffusion
• The hollow abdomen takes in water through the rectum for breathing
• Can force water out the rectum for rapid jet propulsion
• Dragonfly nymphs survive the winter in the water
• Nymphs crawl out on vegetation or boat docks for a final moult that reveals their wings
• Open, undisturbed space is required to stretch or the new wings may end up deformed
• Splitting the skin, unfolding wings and drying may take an hour or more

Adult Appearance Long slender body Two sets of large, clear wings that do not fold Wings lay flat when at rest Large wings are up to 10 cm across Wings are of unequal size Bodies are electric blue, green or red Large eyes cover most of the head Giant dragonflies (76 cm wingspan) exist as fossils 280 million years old

Adult Behavior

• Amazing fliers - hover up and down; forward and back
• Large, compound eyes have up to 28,000 facets or eyelets
• Capture insect prey in flight with a "cage" formed by their dangling legs
• "Patrol" back and forth out over the water
• Wings make a buzzing sound at take-off and landing
• Long-lived from weeks to months

Aquatic Habitat

• Streams
• Slow and still water
• Commonly found in aquatic vegetation in slow currents

Reproduction

• Incomplete metamorphosis includes egg, nymph and adult stages
• Mating pairs are often seen flying with the male holding the female by the neck
• The sexual position of mating pairs form a "wheel"
• The tip of the female's abdomen curls up to remove a sperm pack from the male's abdomen
• Eggs are laid on the water surface or surface of aquatic plants

Nymph Feeding Type Carnivorous Predatory on other insect larvae, nymphs and small fish Nymphs creep within range of prey and then the lower puncher-like "lip" unfolds from under the head and shoots out to grab the victim

Nymph Pollution Tolerance

• Nymphs are moderately pollution tolerant
• Presence in large numbers may indicate fair water quality