(CBS) — Don’t mow the milkweed. Illinois’ official state insect, the Monarch butterfly, needs it.

Because this important pollinator is threatened, the state’s transportation agency is telling maintenance workers to mow no more than 15 feet away from the roadway.

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“Whatever we don’t mow could potentially be habitat,” Stephanie Dobbs, roadside maintenance manager for the Illinois Department of Transportation, tells WBBM.

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The Monarch is believed to look for milkweed near north-south highways during its migration, Dobbs says.

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IDOT boasts this conservation effort comes at no cost.