Monarch and Viceroy Butterflies
Nature Bulletin No. 236-A September 17, 1966
Forest Preserve District of Cook County
Seymour Simon, President
Roland F. Eisenbeis, Supt. of Conservation
MONARCH AND VICEROY BUTTERFLIES
midsummer until frost-time, the Monarch is our best known large
butterfly. It lazily drifts about and is more often caught by children and
amateur naturalists than other butterflies with a zigzag dodging flight. It
is apparently free from attacks by birds, presumably because of its bad
flavor attributed to the fact that its larvae feed exclusively on
milkweeds. Its glowing reddish-brown wings, edges and veined with
black, blend with the mellow colors of autumn fields and roadsides .
Unlike other butterflies, no living Monarch in any stage -- egg, larva,
pupa or adult -- is ever found in our region in winter. In May, ragged
weather-beaten Monarchs begin to appear; now one, then another. Since
the previous fall, their frail wings have carried them many hundreds of
miles south and back again. This butterfly migrates. It follows the
spring back north and lays marvelously sculptured greenish-white eggs
on the undersides of tender young milkweed leaves -- acorn-shaped
eggs about the size of the period at the end of this sentence. In two or
three days these hatch into tiny green caterpillars cross-banded with
black and white, with a pair of thread-like "horns" near the end. For
about two weeks they feed day and night, shedding their skins as often
as they become too tight.
When they are a little over two inches long, they begin to move about
restlessly. Each one finally spins a silken attachment to the underside of
a milkweed leaf or tree branch or an overhanging rock, grasps it by
claspers on its rear end, and hangs head down. In a half day or so it
writhes and twitches out of its old skin to leave a pupa -- a smooth
emerald-green chrysalis beautifully studded with gold flecks; truly one
of nature's brightest jewels, but a helpless thing without mouth, eyes,
legs or wings. As the days pass, the chrysalis darkens because the red
and black adult is beginning to develop inside. Then the pupal skin
splits and, quickly, there is a new Monarch clinging to its old shell, with
wings slowly unfurling like sails. For two hours it slowly opens and
closes its wings as they dry and spread, Finally it goes fluttering away.
That is the miracle of metamorphosis.
Like other butterflies, the adult Monarch uncoils its long tongue and
gathers nectar from flowers. However, it seems to have a special
preference for the milkweed and plays an important part in their
elaborate system of pollination.
The first brood of Monarchs emerges in midsummer and these promptly
lay more eggs on milkweeds. Males and females are similar except that
the male has a small pouch of scent scales which attract the females.
The second brood appears in early autumn but these, instead of laying
eggs, congregate into larger and larger flocks until they finally take off
for the south to spend the winter. Years ago, one such flock -- a half
mile long and a hundred yards wide -- darkened the sky as it passed
over one of our western suburbs.
The adult Viceroy Butterfly belongs to an entirely different family of
butterflies but resembles the Monarch so closely in color, shape and
markings that it serves as a classical example of mimicry in nature. Its
larva feed on the leaves of cottonwood and willow trees, and spend the
winter, as caterpillars, each rolled up in a leaf. The adult Viceroy is a
little smaller than the Monarch, has an extra dark line across the hind
wings, and has a single row of white dots in the black wing borders,
instead of a double row. It is popularly supposed that its outward
similarity to the acrid-tasting Monarch protects it from birds. If so, why
is it that the Monarch out numbers the Viceroy a thousand to one in this
Maybe, as we humans have discovered, it is foolish to imitate.
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Update: June 2012