The Very Hungry Caterpillar

Updated: Aug 22, 2019

By Meagan Breems, Assistant Education Instructor

Central Lake Ontario Conservation

Monarch caterpillars, one of our species of concern, are very picky eaters. They only eat milkweed. All milkweed plants contain a milky-white sap that is poisonous to most animals, but is used by the monarch caterpillar to become poisonous itself!

Last year, the Nature Conservancy reported that monarch caterpillars were observed attaching their chrysalis to the ever-encroaching invasive plant phragmities. Brought to Canada as an ornamental plant, this robust, quick-growing, water-loving bully fills many of Durham Region’s ditches, crowding out our native plant species like the water-purifying cattails, pollinator-providing joe-pye-weed and monarch-food, milkweed.

This year, we have good news! Our Terrestrial Ecologist Diana Shermet, who has been battling the persistent phragmities at Heber Down Conservation Area for a long time now, is finally starting to see progress. Because of staff efforts and our funding partners Hydro One, TransNorthern Pipeline and Enbridge, milkweed and other native species are starting to return to their wetland meadow, replacing the ecologically useless, habitat-destroying phragmities. This year, at a location that was once an impassibly thick stand of phragmites, she was delighted to discover over 20 monarch caterpillars happily chomping on the returned milkweed! Learn more about what you can do to help monarchs...

Chomping down at Heber Down!

Healthy watersheds for today and tomorrow.
Canada Helps Logo

Working in Partnership

Central Lake Ontario Conservation is a

non-profit agency and registered charity: BN: 106887102RR0001

© 2019 by Central Lake Ontario Conservation

100 Whiting Avenue, Oshawa, ON L1H 3T3

Email:, Phone: 905-579-0411