DESCRIPTION: The MONARCH (Danaus Plexippus) is a fairly large butterfly at a wingspan of up to 10 cm (4 inches). It is orange with black veins and margins, with white dots on the margins.
LIFE CYCLE: The whole life cycle of the Monarch is usually completed between 25 and 49 days, depending on the summer temperatures. The cycle starts from the egg stage, then the larval (caterpillar) stage, the pupa (chrysalis) stage, and then to the imago stage (adult butterfly).
The caterpillar stage includes five sub-stages or instars, where the insect molts as it grows. It eats its molt as a nutrient source.
The caterpillar has three pairs of true legs, and five pairs of ‘prolegs’, the last one being at the tail end.
MALE OR FEMALE? The sex of a Monarch is determined upon egg fertilization. It’s not possible to see the sex of a caterpillar unless we dissect them, because the sexual organs are inside their body. But for the chrysalis there’s a way, which is explained (with photos) on the ‘Chrysalis’ page.
As for the sex of the Monarch Butterfly, the male has thinner black veins and two black spots on its hindwings, whereas females have thicker black veins and no black spot. (For photos and more details go to the ‘Butterfly Stage’ page.
Another way of telling apart monarch butterfly males from females is by looking at the tip of their abdomen when they emerge (see the page ‘Emerging as a Butterfly‘ for details and photos).
FOOD SOURCES: The larva (caterpillar) of the Monarch feeds exclusively on Milkweed species. This plant contains substances (cardenolides) that are toxic to their predators, and Monarchs store them in their bodies.
PREDATORS AND DISEASES: In spite of the above protection, Monarchs at various stages of their life are still preyed upon by animals that are immune to the Monarch toxins. The species is also subject to parasitic flies, wasps and protozoa.
DISTRIBUTION: Monarchs are found mainly in North America, from southern Canada in the summer to the mountainous forests of Mexico in the winter. There are various sub-populations such as the western and the eastern ones, which have different migration routes and locations.
Monarchs are also found in New Zealand, Indonesia and parts of Australia, but those populations do not migrate.
A white Monarch morph is also found on Oahu, Hawaii.
MIGRATION: The Monarch butterfly is probably best known for its spectacular migration. For years scientists weren’t sure where it was spending the winter, until butterflies were found by the millions hibernating on Oyamel conifers in Mexican forests.
The most amazing part of this migration is that the butterfly makes the southern trip in ONE generation, barely eating along the way. It needs around four generations to reach its summer grounds the following year.