When you think about all of the amazing animals in this world, you might tend to think about the large furry critters such as bears or moose. Yes, there are many crazy-cool mammals. In fact, there are about 5,000 species in the world.
But at this time of year, when I think about amazing critters, my mind turns to the tiny and delicate monarch butterfly. Yeah, that’s right, a butterfly. Sure, you might be thinking, butterflies are interesting, but are they really all that cool? I would respond, oh, yes, they are.
In late summer the monarch butterfly performs the first of several mind-bending behaviors. All of the monarchs you see in late summer are flying south in a migration no other insect matches. All of the monarchs in the eastern half of the country are heading for the mountains of central Mexico, where they will spend the winter.
How this tiny winged insect manages to navigate thousands of miles to Mexico is still unclear. Millions of monarchs spend the winter clinging to trees and taking short flights on warm winter days. The next spring, they leave Mexico and start to fly north, but they only make it to the southern border states such as Texas. The monarchs then mate, lay eggs and die, never returning to their birthplace.
Adult monarchs only lay their eggs on milkweed. After mating, the female flits around and lands on a variety of plants. She drums the surface of the leaf with her front feet and can identify the kind of plant from the scent that arises from the drumming. If she’s on milkweed, she bends her abdomen around the edge of the leaf and deposits a tiny whitish egg on the underside of the leaf. In a short time, the egg hatches, and a very tiny caterpillar emerges.
The caterpillars feed exclusively on milkweed. Inside the leaves and stems of the milkweed plants is a white milky sap that contains compounds called cardiac glycosides. These cause increased heart rate, increase respiration and a flushed feeling. In some cases, it causes nausea and vomiting.
In short, the milky sap inside milkweed plants is toxic. However, the monarch caterpillar eats the leaves and the toxic sap with impunity. As the caterpillar grows and feeds more and more on the milkweed, the caterpillar itself becomes toxic if eaten by a predator such as a bird.
Eventually the caterpillar matures and seeks out a sheltered spot to change into a butterfly. This is nothing short of mind-blowing. The grown caterpillar spins a silken pad it grabs hold of and hangs down. Its body is slightly curved and looks like the letter J.
The skin on the back of the caterpillar splits open and slides off, leaving a bright green sac, at which point it is called a chrysalis. Inside the chrysalis, all the caterpillar’s cells liquify and reorganize and regenerate to form a completely new life form, the butterfly.
In a short time, the butterfly emerges. The adult monarch flies northward following the spring weather. Along the way, the butterfly feeds and then mates. Each female lays upwards of 500 eggs before she will also perish. The next generation goes through all the same steps to become an adult.
During summer a third and fourth generation go through the same process and eventually make it to the northern tier states and into Canada. It is about the fifth generation of butterfly that will turn around and make the journey south back to Mexico, where its great-great grandparents started.
So at this time of year, if you see a monarch you know this amazing insect is on a mission to Mexico. Without this migratory generation, we wouldn’t have any monarchs next year. What an amazing insect!
Until next time…