Along their migratory routes, monarch butterflies stay nights in certain trees. The “butterfly trees,” as they are called, are carefully chosen – although the criteria exercised in their selection are not known. Species is unimportant, obviously, for at one stopover the roosting tree may be a eucalyptus, at another a cedar or an elm. But, and this is what is interesting, they are always the same trees. Year after year, whether moving south or returning north, monarchs will paper with their myriad wings at twilight a single tree that has served as a monarch motel a thousand times before.
Memory? If so, it is genetic. For you see, the butterflies who journey south are not the ones who come back. Monarchs lay their eggs in sunny climes. Then they die. The hordes who flutter northward in spring are a succeeding generation. Yet, without hesitation, they roost in the same trees as did their ancestors.
Scientists have examined butterfly trees and found them chemically and physically identical to the trees surrounding them. Yet no other tree will do. Investigators have camouflaged a tree’s color, altered its scent. The monarchs were not fooled. Another of nature’s mysterious constants. A butterfly always knows when it is there.” from Tom Robbin’s, Another Roadside Attraction
I came across this butterfly tree while travelling through Kansas.