It is not too often one hears about a good-news infestation. I’d like to come across a bulletin on a new invasive money-tree that was poised to spread through the region. Granted it would produce in foreign currency, but we could make peace with that situation, I imagine.
A money-tree invasion is unlikely, but some areas will soon be overrun by hordes of insects programmed to eat black flies, mosquitoes and deer flies. Dragonflies and damselflies, carnivorous insects in the order Odonata, date back more than 300 million years. Both kinds of insects are beneficial in that they eat plenty of nasties. Of the estimated 6,000 Odonata species on Earth, about 200 have been identified in our part of the globe. I’ve been told it’s good fortune if one lands on you, but the luck is probably that they terrify biting insects.
In late spring I generally get at least one call asking whether it was NY State, Cornell, or the Federal authorities who dumped all the dragonflies out onto the North Country. Dragonflies and damselflies have an unusual life cycle which makes it seem as though someone did release them en masse.
Damsels and dragons lay their eggs right in the water or on vegetation near the edges of streams, rivers or ponds. The juveniles, called nymphs, are monster-like with little resemblance to their parents. You can get a sense of what their choppers look like if you watch the movie Alien. When magnified, you can see the primary jaws of dragon and damselflies open to reveal a second and in some species, even a third, set of hinged jaw-like palps. The only detail missing is Sigourney Weaver.
Dragonflies, powerful fliers, can be so large they can look like a bird at first glance. At rest they keep their wings outstretched, and a line of them basking on a log resemble planes queuing up on a taxiway. A dragonfly’s front pair of wings is longer than its hind, which is one way to tell them from damselflies.
Damselflies are more slender than dragons, and in damsel-like fashion, they fold their wings primly along their bodies while at rest. And although many dragons are colorful, damsels outshine them with bright, iridescent “gowns.” Damselflies are sometimes called darning needles, and even scientific literature lists such damselfly names as “variable dancer” and other descriptive titles.
Damsel and dragon nymphs spend between one and three years underwater where they gobble the soft grub-like larvae of deer flies and horse flies hiding in the mud. They also munch on ’skeeter larvae near the surface, growing larger each year. Depending on the species, a dragonfly nymph can be as long as the width of your hand. Nymphs don’t pupate, but when they are full-grown they will crawl from the water, anchor their “toenails” or tarsal claws into a handy log or boat dock, and open their skin along the center of their backs.
Outdoing any sci-fi film, a graceful dragon or damsel emerges from its monster-skin. After drying its new wings in the sun for a while, these killing machines fly off to eat pests, and also to mate in a precise and complex choreography. Fortunately, dragonfly and damselfly populations are not at risk, even though we kill plenty while driving around rural areas in summer.
It is impressive enough that a fat, striped monarch caterpillar sews itself into a gold-flecked membrane, dissolves into green soup, and emerges two weeks later as a regal butterfly. Dragonflies, though, change within a matter of hours from a water-dwelling creature with gills into an air-gulping high-performance biplane. It’s like having a muskellunge unzip its skin and step out as an osprey.
Because it is triggered by temperature, this extreme makeover happens to each dragonfly or damselfly species all at once. Already several years old, they emerge within a day or two of their age-peers, making it seem as though they materialized out of thin air. Or were dropped as a group out of a plane. I know for a fact that no group or government agency releases dragonflies. But if anyone hears a rumor about exotic money trees being let loose, please drop me a note.
Photo of dragonfly anatomy courtesy Wikimedia user M. A. Broussard.