Monarch madness . Photo by Tom Trower.
Monarch butterflies are the long- ranging kings of insect migration.
In spring, they fly from winter refuges on a few mountaintops in Mexico. In fall, their descendants somehow find the same isolated mountains, where they huddle by the millions in a massive mingling of insects. Even though individuals weigh a half-gram each, boughs bend beneath the masses of butterflies. On a warm day, butterflies cloud the sky. Sadly, the monarch migration may be in trouble.