A dead lyside sulphur (Kricogonia lyside (Godart, 1819): Lepidoptera: Pieridae) was found in Guelph, Ontario, Canada, on 4 April 2011. DNA barcode analysis indicates it likely originated in Texas, United States of America or northern Mexico. The occurrence of this specimen coincided with a very strong weather system extending from southern Texas into eastern Canada on 3–4 April 2011. All possible means of it reaching Ontario are unlikely: natural dispersal, natural transportation on the jet stream, transportation on a vehicle, importation of a pupa on produce, and direct human transport. Unfortunately, there was no way to differentiate between these possibilities.