Science Frictions

Behold the Butterfly

Monarchs flit far afield; other species stick close to home

By Priscilla Long | March 20, 2013
Photo by Joe Mabel

 

The lives of the lepidopterans (butterflies and moths) unfold within the frame of complete metamorphosis. Butterflies lay eggs on the plants their larvae (caterpillars) feed on. The eggs hatch, and the caterpillars eat. And they eat and they eat. And then they shed their furry, leggy, wormy look and pupate—curl up inside a cocoon. In the pupa or chrysalis state the insect does not eat. Birds feed on both caterpillars and cocoons. If you’ve got butterflies, you’ve likely got birds.

Within its cocoon, the pupa morphs into a butterfly. After it emerges, as soon as it can fly, it seeks to mate. Some butterflies, such as the monarchs (Danaus plexippus), migrate hundreds of miles; others remain strictly local.

Butterflies are typically diurnal and love to sun themselves; moths are typically crepuscular or nocturnal. Butterflies have knobs on the ends of their antennae; moth antennae tend to come to a point. A butterfly at rest folds its wings vertically up, with wing undersides facing out; a moth at rest spreads its wings or folds them around its body or into a sort of roof. Overlapping scales cover both butterflies and moths (in Greek, lepido means scale, and ptera means wing). Most butterflies and moths have a long feeding tube for sucking nectar from deep within flowers and this proboscis (pro-BOS-is) curls under the head when not in use.

Butterflies are great pollinators and drink the nectar of many sorts of flowers, but their larvae can feed only on plants they evolved with—often just one kind of plant—and this is one of the great arguments for native-plant gardening. When caterpillars hatch on the wrong plant, they starve to death. If we want monarchs, we must plant milkweed. (And, indeed, those black-and-orange butterflies that look so art nouveau, so like the dream of an artist working in stained glass, need us to plant milkweed. See a report in the March 13, 2013 New York Times titled “Monarch Migration Plunges to Lowest Level in Decades.”) And if we want the western meadow fritillary (Boloria epithore), we must plant violets. If we want the field crescent (Phyciodes pulchellus), we must plant asters. I draw this news from the handsome Timber Press field guide to Insects of the Pacific Northwest by Peter Haggard and Judy Haggard.

(Next week, the lepidopterous passion of Vladimir Vladimirovich Nabokov.)

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