Insects reappear after the cold: Part 2

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StoryImage( ‘/Images/Story//Auto-img-11757120967469.jpg’, ”, ‘The Painted Lady butterfly – Vanessa cardui, is not adapted for extreme cold. Chances are, any Painted Lady you see in Illinois has migrated here from a southern state.‘);
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Spring has arrived, and the insect world is already bustling with activity.

For insects, the most common winter survival strategy is burrowing so they are well insulated from the cold. We think of soil and rotten wood as natural hiding places for these creatures.

But not so obvious is the winter shelter of insects such as dragonflies, mayflies, stoneflies, midges and certain beetles: their larvae survive under ice-covered lakes and ponds. While some of these insects will reach adulthood over a single summer, others may linger in their juvenile stage underwater for as long as six years before coming out to spend a short time as adults. Some aquatic insects, such as mayflies, survive only a day or two out of the water as adults. Others last until fall.

Many aquatic insects remain active throughout the winter, helping sustain hungry fish and visiting waterfowl that pass through on migration routes. Others are only now hatching or awakening from a state of “torpor” or hibernation. Through spring and summer, they’ll be maturing and emerging from the water as winged adults.

Not all insects have adapted to the temperate zone’s coldest temperatures. A few of the insects appearing here each spring are travelers from southern states. They’ve benefited from growing up in warmer regions that allow them a two- or three-month jump on the local competition here in Illinois. Among the earliest and least welcome migrators are the leafhoppers, certain species of which cause damage to crops. Already in the adult stage, these pests arrive searching for young root crops, fruit plants, and various ornamentals on which to lay their eggs.

Beetles, grasshoppers and moths can also be migratory. And much like the leafhoppers, certain species of these insects are pests.

More welcome are the migrating butterflies that will soon be arriving, just in time to drink the nectar of the season’s first flowers. Many butterflies will continue to migrate across North America, with successive generations that eventually reach Mexico by next winter. Among the migratory butterflies of our region are the Monarch, the Painted Lady, the Admiral, the Morning Cloak, and certain species of Whites and Sulphurs (those white and yellow butterflies that are so abundant in wildflowers along the highway’s edge). Some of these butterflies are capable of wintering over here, either as eggs, larvae or adults. Others, such as the Painted Lady and the Red Admiral, are cold sensitive.

from the April 4-10, 2007, issue

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