Butterfly

thingiverse

Monarch butterflies are renowned for an incredible mass migration that brings millions of them to California and Mexico each winter. North American monarchs are the sole butterflies making such a massive journey—up to 3,000 miles (4,828 kilometers). These insects must initiate this journey each fall before cold weather arrives, as it will kill them if they delay too long. Monarch butterflies begin life as eggs that hatch into larvae that devour their eggshells and then consume the milkweed plants on which they were placed. Monarchs are exclusively dependent on milkweed plants for sustenance as their larvae eat almost entirely these plants. Fattened-up larvae develop into colorful caterpillars, then form a hard protective casing around themselves as they transition to the pupa stage. Beautifully colored adult monarchs emerge with black-orange-and-white patterns that make them easily identifiable—and serve an essential purpose. The distinctive color pattern serves as a warning to predators that these insects are unpalatable and toxic. Butterflies that emerge from chrysalides (pupa state) in late summer or early fall differ significantly from those emerging during the longer days and warmer weather of summer. Monarchs born in late summer or early fall are designed to fly, with an innate knowledge due to the changing weather conditions signaling it is time for them to prepare for their arduous journey. They only make one round trip; by the time next year's winter migration commences, multiple summer generations will have lived and died. It will be the great grandchildren of last year's migrators that embark on the trip. Notably, these new generations seemingly possess an innate understanding of their ancestral route and follow the same paths as their predecessors—often even returning to the very same tree. Scientists are particularly concerned about the dwindling eastern population of monarchs, which summer east of the Rocky Mountains. The number of this group is rapidly decreasing due to natural disasters occurring in the Mexican wintering grounds and a sharp decline in the area covered by milkweed plants in their summer habitat.