Dragons are mythological beings common to many cultures. These fearsome predators often share features of a variety of creatures – wings of a bat, head of a reptile, scales of a fish, feet of an eagle, and tail of a serpent. With enormous compound eyes, reticulate wings, long legs, and snaky tail, dragon seems a fitting name for the insects we call dragonflies. Dragonflies belong to a group of flying insects called the Anisoptera. The name Anisoptera comes from the Latin roots aniso- meaning unequal and –ptera referring to wing. Anisoptera is a reference to the fact that the forewings of dragonflies are not nearly as wide as the hindwings.
An empty shed skin attached to a stem is all that remains of the dragonfly's life underwater.
Dragonflies are an ancient clan. Those patrolling the skies 250 million years ago had wingspans of two and a half feet. Modern dragonflies are smaller but no less magnificent. They are active predators hunting and capturing prey on the wing. Spiny legs held beneath the body in a basket-like arrangement trap victims. Small insects such as the mosquitoes or crane flies are common snacks, but larger insects including bees, butterflies, and other dragonflies may be captured. There are reports of large dragonflies catching hummingbirds. Male dragonflies often patrol specific territories along ponds or streams on the lookout for food, potential mates, or other males. Other males entering a territory are pursued and driven away. Females are wooed and mating pairs of dragonflies are often seen flying in tandem. The male sometimes guards his mate while she deposits eggs in the water or on aquatic vegetation. Eggs hatch into curious creatures called nymphs. These small submariners live in ponds or streams. They obtain oxygen from the water through gills found inside their anus. Muscular contractions allow the nymph to pump water in and out of its rear-end to breath. How curious. Dragonfly nymphs capture many kinds of insects such as the larvae of aquatic beetles, midges, and mosquitoes. Crustaceans, worms, tadpoles, and even small fish are fair game for these stealthy hunters. Dragonfly nymphs sit and wait for a potential meal to come near. When the prey is in range, a remarkable, hinged jaw snaps forward like a bullfrog's tongue to ensnare the victim. Nymphs usually move about by crawling slowly. However, when startled or under attack, they expel a blast of water from their rear end and are propelled forward like a jet. After molting several times and completing development, the nymph will climb out of the water and attach itself to a plant or stone. The nymphal skin splits and the adult dragonfly emerges. Once the exoskeleton has hardened, the daring aerialist will take wing to hunt, mate, and entertain lucky humans on a warm summer day.
References
We thank Bill Lamp for providing the gorgeous dragonfly nymphs featured in this Bug of the Week. Information was gleaned from “An Introduction to the Study of Insects” by D.J. Borer, D.M. De Long, and C.A. Triplehorn and “Beginner’s Guide to Dragonflies” by B. Nikula, J. Sones, D. and L. Stokes. For more information on dragonflies, please visit the following web sites.
http://edis.ifas.ufl.edu/IN632