Monarch Butterfly

Four of the many wildlife species that migrate between Canada and Mexico are featured on a se-tenant block of commemorative stamps to be issued August 15, 1995. The wildlife depicted include an insect (the monarch butterfly), a mammal (the hoary bat) and two birds (the northern pintail and the belted kingfisher). The migration habits of each are unique, but all travel for the same reason: to ensure their survival by finding distinct habitats in each country. The monarch butterfly is noted for its bright colours, 76 to 102 mm (three to four-inch) wingspan, fondness for flowers and wide distribution. The monarch is the only North American butterfly that migrates north and south on a regular basis. One of the few milkweed butterflies found in North America, female monarchs lay their eggs on the underside of milkweed leaves. The larvae feed upon the plant's somewhat toxic sap; as a result, the larvae retain this toxicity in their bodies, and predators learn to avoid eating them because they "taste bad". Monarchs west of the Rockies winter in California. Monarchs from east of the Rockies begin their migration to Mexico in mid-September to October, and travel in a slow-moving loose or compact swarm. Dr. Fred A. Urquhart, a Canadian, discovered that in small area in the Sierra Madre Mountains west of Mexico City, monarchs gather by the millions - perhaps 100 million in all. One of his tagged specimens had flown an amazing 2,020 kilometres to Mexico from Chaska, Minnesota. While in Mexico, the monarch butterfly remains in a sluggish state, as the cool weather reduces its metabolic rate so its body maintains the nutrients needed for the return flight northward. While one generation accomplishes the southern journey, it may take three or four generations to return to the original range, arriving in May or early June.