Here is an illustrated checklist for those not yet interested in using formal butterfly guides or participating in a butterfly count. BEWARE: butterflies can be very distracting on nature walks.
Descriptions provided with the photos are when the butterfly is still, usually feeding on a blossom.
The orange and black one we all notice immediately
Smaller and less common than a Monarch
Large with a swallow tail
Small White (Cabbage White)
Everywhere, once you start noticing them
About the same size as Small Whites
One of the early arrivals. Dark brown with white trim
Another early arrival. Dark brown-black with large white spots and orange patches
Orange with black patches, white comma on underside
Unmissable with wings open. Iridescent purple with a few small red spots
Lacey pattern in dark brown on orange
European Skipper (Essex Skipper)
Small orange to brown with forewings usually held at an angle to hind wings – by far the most common
A dull skipper with a large silver patch on underside – larger than most skippers
To be more confident of your observations, a field guide helps with additional and similar species.
“A Pocket Guide to Butterflies of Southern & Eastern Ontario” by Rick Cavasin
“Photo Field Guide to the Butterflies of Southern Ontario” by Ian Carmichael and Ann Vance
For a deeper dive, consider:
“The ROM Field Guide To Butterflies of Ontario” by Peter W. Hall and others, available from The Royal Ontario Museum and Amazon.