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  • Challenge Question #4

    Donna Wimmer (dwimme@mciunix.mciu.k12.pa.us)
    Tue, 11 Mar 1997 19:47:07 -0400

    We think the monarchs know when it is time to leave Mexico by the length of
    daylight. They can determine when to start migrating north by the
    photoperiod. As the days get longer, they realize it is time to leave.
    They also know when to leave by the temperature. As the temperature rises
    for several consecutive days, they know it is time to migrate.

    Donna Wimmer
    87 West Park Ave.
    Sellersville, PA 18960