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| Caterpillar |
Butterfly |
Pupa |
The Monarch is one of the largest Canadian butterflies (wingspan: 93 to 105 mm). The upperside is bright orange with heavy black veins, and a wide black border containing a double row of white spots. There is a large black area near the wing tip containing several pale orange or white spots. The underside is similar except that the hindwing is much paler orange. Males have a sex patch, a wider area of black scales on a vein just below the centre of the hindwing.
Abundance: The Monarch varies greatly in abundance from year to year, depending on the weather conditions, which affect both reproduction and migration, as well as on their survival rate over the winter. The populations usually build up through the summer through several generations. In the early fall they can be seen in the hundreds or thousands at places where the southward migration is concentrated, such as at Point Pelee, in southwestern Ontario, and Presqu'ile Provincial Park on the north shore of Lake Ontario.
Flight Season: Occasionally the Monarch arrives in Canada towards the end of May, but the bulk of immigrants arrive in June. They then pass through two or three generations before the bulk of the population leaves in September, although stragglers will be seen well into October and even November.
Habits: The Monarch is the best known of all migratory butterflies, and the only one with a well-documented return migration. Its migratory tendencies enabled it to spread over most of North America in the 1800s, probably coinciding with the clearing of the forests of eastern North America and a vast increase in the population of both Common Milkweed (Ascleptas syriaca) and Monarchs. All Monarchs from west of the Rockies fly to a few small areas of California, a fact that has been known for more than a century; Pacific Grove, near Monterey, California, is famous for its congregating Monarchs. All other North American Monarchs, from Alberta to Newfoundland, travel even farther, to about 30 tiny overwintering sites in a small area of the Transverse Neovolcanic Belt of Mexico, between 70 and 170 km west of Mexico City (Brower, 1995). All the sites are in forests of Oyamel Fir (Abies religiosa, Pinaceae); the Oyamel Fir forest is a specialized high-altitude ecosystem on the higher peaks of Mexico. In these sites, at altitudes of around 3000 metres, where the temperature usually stays just a few degrees above freezing all winter, the Monarchs pass the winter hanging on the trees in such numbers that they sometimes break large branches by their weight. Estimates as high as 14 million butterflies have been made in the few acres of one such site.