General information about the Monarch butterfly.

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.

This Monarch caterpillar will soon turn into a chrysalis - © Denise Motard
Monarch caterpillar ready to turn
into a chrysalis

MALE OR FEMALE? Please check this page for ways of finding the sex of a Monarch caterpillar or butterfly.

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. For more information please check this page on PREDATORS.

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, in addition to the regular orange-colored ones. (Below are photos of monarch caterpillars munching - voraciously! - on milkweed-related plants in Lanai, Hawaii - photos by Caroline St-Laurent).

 MIGRATION: The Monarch butterfly is probably best known for its spectacular migration. For years scientists were not 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 in southern Canada the following year.

THREATS: One main threat to the Monarch butterfly is the eradication of its food source, Milkweed, in the USA Midwest. In industrial agriculture, this plant is considered a pest in fields of soy and corn and is treated with pesticides.

Another important threat is the illegal logging of trees in its wintering grounds in Mexico. Some farmers and also criminal gangs cut the trees to grow avocados, which is a lucrative crop.

There is also the spread of diseases and parasites in the wild Monarch population, sometimes from Monarchs raised in 'farms'.

Finally, climate change is starting to have a negative influence on the Monarch population levels and may have an impact of this butterfly migration patterns.