Return to the Wild - Evolving perspectives on Canadian wildlife
The monarch butterfly has been recorded in all of Canada's ten provinces.

Did you know?

The monarch possibly has the longest insect migration in North America, travelling up to 4,000 kilometres a year.

Scientific name: Danaus plexippus
Average weight: 1.5 g (caterpillar)
0.4 g (butterfly)
Average wingspan: 93–105 mm
Average lifespan: 6–8 weeks (summer generation)
6–8 months (winter generation)
A monarch butterfly perches on top of a flower.

About

Biology

The monarch butterfly’s bright colouring is famous, but also functional: it warns predators that it is poisonous. Even monarch larvae or caterpillars have bold black, yellow and white stripes. This is unlike most immature butterflies, which tend to blend into their environments.

The adult monarch has vibrant orange wings with a thick black border surrounding two rows of white spots. The male can be differentiated from the female due to two obvious black spots on his hind wings. As well, a female monarch has wider bands of black on her wing veins.

The monarch’s colouring, though unique, is not exclusive. The orange and black viceroy butterfly looks very similar. However, it is a little smaller than the monarch and has a black stripe that crosses the bottom of its back wings.

Habitats and behaviour

It is also known as the “milkweed butterfly”, since this plant sustains key stages of the monarch’s life. It acts as a home, as food for the caterpillar, and as a breeding ground for the adult butterfly. Feeding on the milkweed is also what makes the insect toxic, protecting it from predators. It should be noted that adult butterflies eat milkweed less often and thus lose some of their toxicity as they age, yet milkweed is the only plant that monarch caterpillars will eat.

This predilection for the milkweed is one explanation as to why the monarch migrates over such a wide range. Starting in Mexico, it is believed both the milkweed and monarch evolved, and as the milkweed extended its range and moved north, the monarch followed.

A monarch also migrates because it can only live in warmer climates and is unable to survive frost. Usually it looks for dense tree cover in an overwintering spot. It can travel thousands of kilometres due to its ability to conserve energy, either by riding columns of rising warm air, or depending on strong winds that raise it up to altitudes of one kilometre above the ground. And yet, despite this obvious evidence of the monarch’s formidable navigational skills, its underlying mechanism remains a mystery to us.

During reproduction the female monarch lays a fertilized egg on the underside of a milkweed leaf. A single female monarch may lay as many as 400 or more eggs over her lifespan, one at a time. From there, the butterfly goes through four stages of transformation called metamorphosis and this takes around 30 days to complete. After spending 3 to 12 days as an egg, it hatches as a larva or caterpillar. Its job then is to eat and eat, until three weeks later when it attaches itself to a twig. While attached, the naked pupa takes on a vase-like shape. From here, the monarch enters the third stage as a gold speckled, jade-green pupa. Less than two weeks later, a fully formed adult butterfly emerges.

Range

Although the monarch butterfly has been recorded in all ten Canadian provinces and the Northwest Territories, there are two very distinct populations in North America — one in the East and one in the West. The western population includes monarchs west of the Rockies that winter in tree groves on the coast of California. The larger eastern population occurs east of the Rockies, from southern Canada down to the Gulf Coast of the United States. It winters in the mountain fir forests of central Mexico.

Monarchs have been found in Western Europe (rare), Australia, South America and several Pacific islands including Hawaii.