The monarchs that fly to Mexico are a different generation
Most MONARCH butterflies live about a month. But the ones that hatch in late summer in North America emerge in a different state altogether: they do not breed, their bodies store fat instead, and they live for eight months. They are sometimes called the Methuselah generation, and they are the ones that MIGRATE — up to 3,000 miles to a handful of mountain forests in central Mexico, to trees their great-great-grandparents left the previous spring.
How they find them is the good part. They navigate by the sun, which means they need to know the time of day to correct for it moving — and the clock doing the correcting sits in their ANTENNAE, not their head. Butterflies with their antennae painted over lose the ability to hold a heading, while ones that can still see the sun perfectly well but have no working clock set off in the wrong direction entirely.
They taste with their feet
A female butterfly landing on a leaf and scrabbling at it is not fidgeting. Her front feet carry taste receptors, and she is drumming hard enough to break the surface and sample the sap, checking she has found exactly the right plant before laying her EGGS — because her CATERPILLAR may be able to eat only that one species and cannot travel to find another.
The adult's own eating is done through the PROBOSCIS, a drinking straw kept coiled like a watch spring under the head and unrolled into a FLOWER for NECTAR. It is not a single tube but two grooved halves zipped together, and a butterfly that fails to zip them properly on emerging will starve. Several kinds skip flowers altogether and feed on rotting fruit, tree sap, or mud puddles, from which the males take salts.
The difference between a moth and a butterfly is not real
Everybody knows the rules: butterflies fly by day and are COLORFUL, a MOTH flies at night and is brown, butterflies hold their WINGS up and moths lay them flat, butterflies have clubbed ANTENNAE and moths feathery ones. Every one of those has plenty of exceptions.
The deeper problem is that moths are not a group. Butterflies are one particular branch that grew out of the moths, so a butterfly is a kind of moth in the same way a human is a kind of ape — which makes 'moths and butterflies' a bit like saying 'apes and people'. The split survives because it is useful in a GARDEN, not because nature drew it.
What the patterns are for
Those WINGS are roofed in thousands of tiny overlapping scales, which is what comes off on your fingers as dust — and the looseness is deliberate, letting a butterfly tear free of a spider's web leaving only scales behind. The PATTERNS on them are doing several jobs at once.
Big round SPOTS near the edge of a wing take a bird's strike away from the body, and butterflies are regularly found flying happily with beak-shaped holes punched through exactly there. Bolder eye-spots suddenly flashed open startle a predator outright, an effect confirmed by watching birds flinch. And the dull underside of a folded wing turns the whole insect into a dead leaf. The rest of the grid — the PAINTED lady, the SWALLOWTAIL, the CHRYSALIS and COCOON, the PUPA and LARVA, the FLUTTER across a GARDEN — is the familiar part.