Dr.Chip Taylor teaches biology at a university in the United States.He studies one kind of North American butterfly.Just like a migrating bird,this butterfly travels about 4 000 kilometres south in fall.Fantastic facts about the butterfly have been drawing Dr.Taylor's attention.
In Mexico,the butterflies always return to the same small piece of forest,which is only 20 kilometres wide.Here,as many as 230 million butterflies spend the winter.They can cover some trees almost completely.The butterflies that return to the south are the greatgreat grandchildren of the butterflies that left for the north.When they begin to travel north in spring,the females lay eggs.They lay eggs on only one plant:milkweed.
But in Mexico,people cut down the trees that the butterflies need to rest on because they want more land for farming.In the United States and Canada,farmers use chemicals that kill milkweed.This worries Dr.Taylor a lot.
Now things are improving.Mexico has begun to protect parts of its forests.The United States and Canada have encouraged farmers to use less chemicals.
Scientists still don't understand how the butterflies know when to fly south.If they are even a few days late,they will freeze.And how do all the great-great grandchildren find the same forest in Mexico every year? This is both puzzling and interesting for many scientists.
There are many mysteries yet to be discovered by those interested in science.Would you like to study biology?