The common name “monarch” was first published in 1874 by Samuel H. Scudder because “it is one of the largest of our butterflies, and rules a vast domain”. But the name may be in honour of King William, Prince of Orange.

The caterpiller stage lasts around 2 weeks. These toxic species, monarch (Danaus plexippus) caterpillars, usually advertise themselves with brightly striped or coloured in black, red and yellow—the danger color. Any predator that attempts to eat a caterpillar with an aggressive defence mechanism will learn and avoid future attempts.

In the pupa or chrysalis stage, the caterpillar spins a silk pad on a twig, leaf, etc., and hangs from this pad by its last pair of prolegs. It hangs upside down in the shape of a 'J', and then molts, leaving itself encased in an articulated green exoskeleton. At this point, hormonal changes occur, leading to the development of a butterfly (metamorphosis). The chrysalis darkens (actually becomes transparent) a day before it emerges, and its orange and black wings can be seen.

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