Thousands of colorful visitors are passing through Iowa on their way south.Iowa State University entomologist Donald Lewis says monarch butterflies arein the midst of their annual treck to Mexico.He says you may see the butterflies stopping in your backyard for a littleenergy boost as they take nector from flowers.Lewis says it’s unlikely you’ll see the same butterflies on the return tripas these adults will die, but their offspring will return when it turns warmagain.Lewis says the butterflies will return in late April or early May.