Tag Archives: butterflies

author - Scallen, insects/spiders

Monarch Butterfly- RIP 2026

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by Don Scallen, Vice-President

The eastern migratory population of monarch butterflies is no more. Lepidopterists (butterfly and moth scientists) confirmed earlier this year, that the once familiar orange and black butterflies are essentially extinct. Their awe-inspiring north-south migrations, linking Mexico, the United States and Canada have ceased.

Most of us are old enough to remember when monarchs were a frequent sight in meadows and gardens. The monarchs’ demise was not unexpected. For decades, people in all three North American countries ratcheted up their assaults on these iconic insects. The monarchs’ overwintering sites in the oyamel fir forests of Trans-volcanic Mountains of central Mexico, while nominally protected, were steadily reduced in size by illegal logging.

Criminal gangs with the tacit assent of corrupt government officials plundered the forests under the cover of darkness.

At the same time, land use practices in North America conspired to reduce milkweed, the monarchs’ larval food plant. Round Up, a potent herbicide was sprayed on thousands of hectares of genetically altered “Round-up Ready” corn and soy, eliminating all of the milkweed in and around agricultural fields.

Homeowners throughout North America could have extended a helping hand by growing milkweed for monarch caterpillars and offering flowers with abundant nectar to the adults. Most people however, in thrall to their lawns, continued to primp and preen those biological wastelands at the expense of birds, butterflies and bugs.

The monarch is dead. No longer will it startle with its beauty. No longer will it inspire with its improbable journey from Canada to Mexico. And no longer will the imaginations of children be carried aloft on its gossamer wings.

Postscript:
In 2006 at a monarch overwintering roost in Mexico I met Lincoln Brower, a pre-eminent monarch butterfly researcher from the United States. He predicted that the eastern North American monarch – our monarch – had “about twenty years left”. I fervently hope he was wrong, but with populations this year at their lowest ebb ever, his dismal forecast may come true.

Read more by Don Scallen at his blog, Notes from the Wild

author - McIlveen, climate, insects/spiders

Giant Swallowtails and Climate Change

Recently, one of the items covered by the news media was the change in distribution of various species owing to climate change. There are other causes for expansions of populations other than climate shifts but this discussion is limited to the global warming phenomenon. The media accounts included the recent appearance of fish species in the ocean much further north than where they normally occur. One species that was mentioned that has relevance to our own area was the Giant Swallowtail Butterfly.

Figure 1: Giant Swallowtail Butterfly adult, Prince Edward Point, May 30, 2009
Figure 1: Giant Swallowtail Butterfly adult, Prince Edward Point, May 30, 2009

While it is a good thing that the media covered this important story, they unfortunately got it wrong. To listen to what they were saying one was left with the impression the species involved were fleeing from excessive heat in their traditional areas and seeking respite in cooler areas. This is not the case. The geographic range expansion is possible only because the new areas are now offering conditions (slightly warmer) where the cooler conditions had prevented then from surviving before. Giant Swallowtails (Papilio cresphontes) are the largest butterfly in much of North America. Their wingspan ranges from 10 to 14 cm across! (Figure 1). They tend to stay in woodland areas or, in the southern US, in citrus groves. The adults sip flower nectar for food. The larvae of this butterfly are known as the ‘Orange Dog’, not for their colour but for their host in citrus groves. The caterpillars look a lot like bird droppings and can get as big as 4.5 cm long! (Figure 2)

They generally adopt a disguise by looking like bird droppings, an appearance that they retain until they pupate. Another deterrent to would-be predators is the osmeterium. This is a reddish, forked gland located behind the head that is extended when the caterpillar disturbed. The osmeterium exudes a fluid that is considered to smell terrible and deters any attacker.

Figure 2. Giant Swallowtail Butterfly larva on Common Hop-tree seedling, Windsor, September 6, 2011
Figure 2. Giant Swallowtail Butterfly larva on Common Hop-tree seedling, Windsor, September 6, 2011

In years past, Giant Swallowtails were essentially restricted to the far southern parts of the province. They would occasionally wander farther and one vagrant had been reported at Ottawa. Now they are much more frequent in parts of the province where they were seen only occasionally. How much of this recent range expansion is due to climate change is still unclear. Milder winters could certainly assist in the survival of the species over the coldest part of the year. A key limitation in their distribution is the availability of their host plants.

Hosts of the Giant Swallowtail all belong to the citrus plant family Rutaceae. We do not have many groves of oranges or lemons in Ontario to sustain the butterflies but we do have a few other members of the plant family. The list includes Gas Plant (Dictamnus albus), Cork Tree (Phellodendron amurense), Common Rue (Ruta graveolens), Common Hop-tree (Ptelea trifoliata) and American Prickly-ash (Zanthoxylum americanum). The first three mentioned are all introduced or non-native species. They are rarely grown and are thus hardly capable of sustaining populations of the butterflies in Ontario. The Hop-tree is rather uncommon in Ontario and restricted to the Carolinian zone. The main job of supporting the larvae of the Giant Swallowtails then falls to the Prickly-ash that has a much wider distribution than the others though it also tends to grow in more southern parts of the province. Prickly-ash is a relatively inconspicuous species that goes unnoticed unless one needs to cross through a patch of it. Then the thorns on its stems are more than adequate to grab the traveler’s attention. Other than vagrant butterflies that might be carried by the wind, the anticipated range of the butterflies is going to strongly mirror the distribution of Prickly-ash. Perhaps the changing climate will allow that plant to extend its range and thus allow the butterflies to follow further a field. It will be interesting to follow shifts in distribution patterns for these species as well as others that exhibit similar types of range restrictions.

by W.D. McIlveen
Halton/North Peel Naturalist Club