About the Ontario Butterfly Atlas

..maps...display of records...flight season charts


The Ontario Butterfly Atlas is a project of the Toronto Entomologists' Association. Atlas data is used in preparing the TEA's annual seasonal summaries (Ontario Lepidoptera). The TEA has been accumulating records and publishing seasonal summaries for more than 50 years, with the first edition appearing in 1969. The first maps appeared in the TEA's Ontario Butterfly Atlas book, published in 1991. The present interactive web-based maps started in 2011. The database of records supporting the maps has grown from 65,000 in 2011 to over half a million today. The Atlas is updated at least once a year. The latest update was in January 2023.


Atlas data comes from e-butterfly records, iNaturalist records, and records submitted directly to the TEA. Some data is from other sources (e.g., ROM, other museums, BOLD, BAMONA). For all of these sources, some records are not included in the Atlas; see this page for details. Data from butterfly counts is included only to the extent that individual observers at the counts report their data through these channels.


About 35,000 records were added to the Atlas for the year 2022. The sources of 2022 Atlas records were: 83% from iNaturalist; 9% from e-butterfly; and 8% from direct submissions of records on spreadsheets to the TEA. When the atlas started, direct submission was the top source of records. eButterfly was the top source of records in 2017 and 2018, but iNaturalist took over the top spot after that. For more details on sources of data, and their pattern over time, see this table.


The real names of observers, rather than iNaturalist and e-butterfly userIDs, are included whenever they are known to the TEA. Where only the userID is known, this is included in square brackets in the "observer" column.


One species currently existing in Ontario, the Mottled Duskywing (Erynnis martialis), has been classified as endangered by federal and Ontario governments. For this species, recent observations from areas with extant colonies (along with any associated observations of other non-endangered species) are only shown on county and zone level maps. They are not shown in maps of 10K squares, parks or circles.


We thank Bird Studies Canada for providing the shape files defining the 10,747 10 km squares shown on these maps. The shape files for counties and parks are from Ontario's Land Information Office and contain information licenced under the Open Government Licence - Ontario.


See also the TEA's Ontario Moth Atlas.


There will be inevitably be some errors or questionable observations, and we would like to know about this. We also welcome any questions about the atlas or suggestions for improving it. Contact the TEA (Alan Macnaughton, info@ontarioinsects.org).


In publications or other research use of this data, use the following citation: Alan Macnaughton, Ross Layberry, Rick Cavasin, Bev Edwards and Colin Jones. Ontario Butterfly Atlas (Supply date accessed here).