Monarch butterflies are unique -- they're the only butterfly to travel thousands of miles when the seasons change. They travel from as far north as Canada all the way down to a few very specific mountaintops in central Mexico. They don't have a car, or an airplane ticket. They just have their two little wings. So we're asking: How do they do it? How do they migrate thousands of miles? And why? We'll also look at why other insects don't have to travel south for the winter -- hint: it has to do with something in their blood. Of course, we have a mystery sound for you to decipher, too.