Things with Wings: Six-Legged Shape-Shifters

By Joseph Mooney

Our final Things with Wings focuses on metamorphosis—basically Greek for “change shape.”

Many insects undergo metamorphosis. There are two kinds of metamorphosis: complete and incomplete. Monarch butterflies, for example, completely metamorphose, from egg to larva to pupa to adult. Another (incomplete) metamorphic creature is the cicada. Some cicada species spend years underground as nymphs (a kind of larva). Eventually they emerge to shed their nymphal shells and become adults that sing, mate, lay eggs, and die—all in the space of a few weeks. Makes you wonder about the meaning of life!

Pictured: a dragonfly adult laying eggs in the water (photo by C.L. Goforth); dragonfly eggs; stages (instars) of dragonfly nymphs.

A familiar metamorphic critter is the dragonfly. Like the cicada, a dragonfly’s full life span may last several years, but very little of that life includes time as an adult.

In the steady crawl to metamorphosis the dragonfly’s life cycle encompasses three stages: the egg, the nymph, and the adult dragonfly. After mating, a female dragonfly lays her eggs in a lake, pond, or wetland. The eggs eventually hatch out as nymphs, and the nymphs themselves go through several stages (instars). The dragonfly lives out most of its life cycle as a nymph.

The nymph is equipped with gills that take in oxygen from the water. Nymphs also have the appetite of a carnivore,  gobbling bugs, grubs, even fish. Beneath the waves, nymphs move through a series of instars for a period of a few months to several years.

In its final instar the dragonfly nymph emerges from its watery nursery and anchors itself to a reed. Hours pass as the nymph’s shell splits and the adult begins to emerge. Using gravity as an aid, the dragonfly pumps fluid from its body into its wings. At last the glistening wings are strong enough to launch the insect aloft, and the dragonfly takes flight.

Thanks to all who’ve sent in their photos of things with wings! We will publish the photos later this month.

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