A large crowd gathered January 17 for a Mississippi Valley Field Naturalists (MVFN) lecture on Monarchs presented by Jean Lauriault of the Canadian Museum of Nature. As one of Canada’s foremost Monarch experts and member of a tri-national committee for conservation of these animals, Lauriault knows Monarchs well. Monarchs (Danaus plexippus) have a very interesting life cycle, as short as 20 days, or 9 months long. During a hot summer the cycle is quick and thus more generations are born. From June to August, adults lay eggs on milkweed. In 3 to 15 days they hatch and there are 5 instars or molts of the caterpillar (larvae) taking up to 14 days, before the pupa or chrysalis (not cocoon) stage is reached. The adults emerge within 7-15 days and will live as little as 14 days or as long as 8-9 months for the late-season adults emerging in August. These are the adults which go into sexual diapause and begin the amazing migration south, remaining sterile until starting their return trip.
Monarch migration has always fascinated scientists, children, and nature lovers alike, but it wasn’t until 1975 that the site of their winter home in Mexico was discovered. As they leave Canada, Monarchs in Ontario gather at ‘staging’ areas to cross Lake Erie and Ontario. Then, covering distances of up to 100 km per day at heights of up to 1 km, they head to locations in southern US and remote areas in Mexico. Little is known about the stopover locations used during their trip, but upon arrival as many as 50 million butterflies may congregate within trees in a single hectare. They do not eat all winter but survive on stored Lipids. In March as the area gets drier, they mate and head north, with many stopping in Texas to lay their eggs and die, leaving the next generation to complete the return journey. Those arriving in Canada are the children of those that left in August.
It is hard enough to conserve a species that stays put, but conserving Monarchs, Lauriault noted, poses a ‘super challenge”, requiring the efforts of three countries. Concerns in Mexico include protecting the remote wooded area favoured by the Monarch, from illegal logging. When return migration commences clouds of butterflies fly low over the land and thousands/millions may be killed by vehicles. Important also are the stopover areas in the US, many not yet identified, where a generation may be raised in the spring, and where non-migrating Monarchs may also live.
What can we do here in Canada to conserve Monarchs? The staging areas in southern Ontario need continued protection. Secondly, Milkweed, the sole food of the caterpillar, is classified as a weed since it is toxic to cattle; action needs to be taken to remove this classification. A very aggressive invasive species that has gotten a strong foothold in Ontario is dog-strangling vine (Pale Swallowwort), also in the milkweed family. Adults can mistakenly lay their eggs on it, but the hatched caterpillars cannot eat this plants leaves. Dog-strangling vine should be eradicated whenever possible. Finally as Lauriault pointed out, the adult butterflies feed on nectar of various wild flowers and thus roadside flora need to be protected from mowing and herbicide application. On an up note, provide habitat by planting a butterfly garden, and enjoy!
To wrap up our evening, we presented Jean Lauriault with a Monarch T-shirt. He then drew a name for a second Monarch shirt, won by Teresa Peluso. Both shirts were donated by Neil Carleton, a local educator who often uses Monarchs for teaching biology and conservation in his classroom.
The next lecture in our series “Our Natural World: Conservation Challenges” on Thursday, Feb 21st will be “Ontario’s Birds” presented by Cliff Bennett, an MVFN founding member and Ontario East Director for Ontario Nature. For more information please contact Program Chair Joyce Clinton at 613-257-4879 or email . MVFNs Annual Winter Walk will take place February 17th. Learn about Winter Adaptations of Plants and Animals. For more information call Cliff Bennett at 613-256-5013 or refer to www.mvfn.ca for information on either of these upcoming events.
1. Further information on butterflies can be found in The Butterflies of Canada by Layberry, Hall and Lafontaine, parts of which can be found on-line at http://www.cbif.gc.ca/spp_pages/butterflies/index_e.php.
2. More information on dog-strangling vine may be found at http://www.swallow-wort.com, and http://www.ofnc.ca/fletcher/research/swallowwort/index_e.php.