05/12/2022
Butterflies in Winter
Have you ever wondered how butterflies survive Manitoba's cold winters? Some are "snow birds," like some of us, and head to warmer weather. The most famous example is the Monarch butterfly that winters in Mexico. Monarchs start returning north sometime in March but go through one or two generations on migration before making an appearance in Manitoba, usually in June but sometimes in late May.
Butterflies spotted earlier in spring probably overwintered as adults. Nooks and crannies in trees, old buildings, and other protected spots are common sheltering places. The Mourning Cloak butterfly is one of the earliest butterflies to be found in Manitoba, often emerging in April. Milbert's and Compton Tortoiseshell butterflies also make an early appearance. These early butterflies have an interesting spring diet that might include tree sap, owl pellets, and animal dung.
Some butterflies overwinter as chrysalises (pupal stage). Instead of the obvious jade-coloured chrysalises of Monarchs, many of these have evolved to blend in with their surroundings to avoid being eaten. Black swallowtail caterpillars attach themselves to twigs on shrubs and transform into chrysalises that look like just more twigs.
Other species, such as some of the hairstreaks, use the strategy of overwintering as eggs. An insulating cover of snow protects the eggs from drying out in the cold winter air.
The most common method for butterflies to survive the Manitoba winter is in the larval stage, as a caterpillar. Sugar-like compounds in their blood serve as antifreeze to protect them against sub-zero temperatures.
While adult butterflies vary in when they can be seen, June and July are the best times to find butterflies in Manitoba.
Did you know that over 150 species of butterflies have been found in Manitoba? A good source for more information is Manitoba Butterflies: A Field Guide by Simone Hébert Allard (Winnipeg, Turnstone Press, 2013).
Photo by Marilyn Latta (6 April 2021, Henteleff Park).
