They feed on aphids not plants. Monarchs have been known to migrate over 3000km. In fact a Monarch tagged at Presqu'ile, here in southern Ontario, was recovered in Mexico and is on record as being the longest insect migration. Butterflies don't have lungs. The larvae of some of the some Blues, Coppers and Hairstreak butterflies produce a sugary excretion that is consumed by ants that in turn protect the larvae from predators.
Butterflies taste with their feet.
The Monarch's Mexican wintering site was only discovered in 1975. The Mourning Cloak and Compton Tortoiseshell are Canada's longest lived butterfly. They can last up to 11 months. Pine Elfins are among the few butterflies, worldwide, that use evergreens as a host. Monarchs can fly a 1000km without stopping.