If you would like to begin to recognize some of the butterfly species of Middlesex County, but are not ready to purchase a field guide or submit photos to iNaturalist, start here.
BEWARE: butterflies can be very distracting on nature walks.

Large – May to October

Medium – June to September

Large – May to September

Small – April to October

Small – May to October

Medium – April to October

Small – April to October – underside is very different

Small – April to October – white comma on dark underside

Small – June to August – less vibrant underside

Small – May to September

Small – June to July

Small – silver on underside only – June to August
When you see a butterfly unlike any of the photos, congratulations! You are certainly going to see some of them on an organized butterfly count. It may be one of the following:
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
“Southern Ontario Butterflies and their Natural History” by Jay Cossey.
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.
Online resources can be found at:
https://www.ontarioinsects.org/
https://www.ontariobutterflies.ca/home