they live. But there is a very big exception. The last generation of butterflies, hatched before the fall migration southward, is gifted with a much longer lifespan of about eight to nine months. This allows them to fly for as long as two months to get to their winter home, survive the winter in a state of torpor and revive in spring to begin the journey back north. While many of these “Methuselah generation” butterflies last


only long enough to lay their eggs on the first milkweed they come across on their journey home, their children and some- time their grandchildren will carry on to reach the ultimate goal. Some say, however, that as many as 10 percent, make the 2,000 to 4,500 km round trip, travelling at speeds of around 19 km per hour and covering 50 to 75 km per day. At the end of their journey, they lay eggs for the next generation and then succumb. Leaving Canada in August, September and October they


arrive in Mexico two to three months later, aided in their flight by warm air currents and wind. They are reproductively dormant (in diapause) during this migration, concentrating on making it to the south. “A variety of signals from nature combine to induce this diapause condition, including shorten- ing day length, changes in temperature between daytime and night time, and even the age of the milkweed plants that they ate as larvae,” says the Monarch Wildlife Fund in the U.S., where there are several organizations working to save the monarchs. When the butterflies reach their destination, they go into torpor, in effect sleeping through the cold winter months under the fir trees, protected from deadly wet and cold. As the days begin to warm in February and perhaps respond-


Notice the second black ring on the butterfly above. This one is a Viceroy.


Viceroy: The Monarch mimic


known for using this ruse to protect themselves from predators. Monarchs have their own mimic: the viceroy


A


butterfly that looks very similar to the untrained eye being the same colour with very similar markings, but it has a secondary black ring on the centre of its wings that distinguish it from the larger Monarch. Another example of this mimicry is that both the


Red Spotted Purple and the Eastern Tiger swal- lowtails mimic the Pipevine swallowtail which is unpalatable because it eats the distasteful climbing Dutchmans’ Pipevine. It contains a toxin that affects kidneys and is a potent carcinogen. For its part, the Giant swallowtail mimics bird


droppings at its earliest instars after hatching. There are many other instances of this mimicry in nature, including among mushrooms, which his why you should heed the advice to go mushroom picking with the oldest mushroom picker you know! Viceroys do not migrate but overwinter as larvae


rolled up in a leaf of the willow or poplar, their host plants, emerging about 15 days after the trees have leafed out.


18 • Early Spring 2014


n age old trick of in nature is that of playing the mimic. Butterflies and their larvae are well


ing to what may be a signal from the awakening milkweed, the monarchs begin stirring. About half the population stays in Mexico but of most of those that will migrate have left by the end of March or early April, arriving here in Canada as early as May. Diapause ends with the urge to migrate and as these butter-


flies become sexually active they lay eggs along the way, passing on the torch to the next generation to complete the journey. A few, as mentioned above, make it all the way back and the


earliest arrivals could be first generation butterflies that may look quite faded and worn out when they get here. Let’s plant milkweed


Milkweeds and monarch butterflies are like intrinsically


linked. Monarchs rely on milkweed to sustain their larvae and to protect the next generation by making caterpillars and butter- flies toxic to a number of predators such as most birds. The toxic material, a poison called cardiac glycosides, affects the heart of vertebrates, but it does not harm many predatory invertebrates.


Monarchs and trees M


onarchs, as they prepare for their journey south in the fall, demonstrate a behaviour called roosting. They


will collect in small groups or in masses, collecting high up in certain trees, staying sometimes for a short period and other times for a day or two. They may be resting or building up resources from a nearby nectar source, nobody knows for sure. We do know however, that they do not fly at night, travelling only during the day. Nearly all monarchs roost in trees, although they have


been observed roosting in tall grasses, especially in Texas. The trees included pines, conifers, maples, and oaks in the north and pecans and willows in the southern regions. They like to be near water and a ready source of nectar such as a field of goldenrod.


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