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2015-10-01

The Monarch butterflies are coming

By John Hegemier Director, Bandera Library

Monarch butterflies pass through Bandera County in October as they migrate to Mexico. Don't mow the milkweed until they have all passed, as it is one of their key foods.



Keep your eyes open. The season is almost upon us. The Monarch butterflies will be passing through Bandera County this October. Their numbers will be peaking midway through the month. When you see one of these brightly colored creatures fluttering by, you are witnessing a member of the only known insect species known to complete a two-way migration. And what a fascinating migration it is.
The butterflies passing through Bandera County and the Hill Country this October are the fourth and last in a multi-generational migration story. It's this generation that has the longest and most interesting life cycle.
Whereas the first three generations of Monarch butterflies typically only live about six weeks, this last generation needs to live eight months to accomplish all the tasks that need to be done. These little insects begin their life in the middle and eastern parts of North America and travel all the way to the Sierra Madre Mountains of central Mexico where they will overwinter. Sometimes they travel up to 80 miles in a single day.
Tourists will travel from around the world to see this amazing congregation of butterflies. Millions and millions of Monarchs gathered together in the same valleys as their ancestors. The temperature and humidity of the Sierra Madre Mountains suits their needs and allows them to wait out the cold winter.
Once spring arrives, these long lived butterflies start to journey again, this time heading northward, laying eggs along the way. Four days after these eggs are laid small caterpillars will emerge, eventually becoming the first generation in another migration story. Two more generations of Monarchs will complete their life cycle, continuing the northward journey until fall arrives and the fourth generation begins the long journey back to the Sierra Madre Mountains.
How do the Monarchs know what to do? Nobody knows the exact mechanism that guides this journey, but some kind of genetic memory, combined with environmental cues seems to provide the impetus for this amazing journey.
One thing is certain though, the Bandera Public Library is celebrating the return of the Monarchs this fall. The library staff has set up a display of butterfly books that describe this migration in more detail. We also have books for youngsters that describe the butterfly life cycle. We have provided pictures of butterflies that the little ones are encouraged to color. We will be displaying their art work till the Monarch butterfly migration has passed.