Mustard White (Pieris oleracea) 

Member of Family: Pieridae  

The spring generation of this species has darker scaling on the underside than the summer generation (compare upper left and upper right images). The individual shown at lower left, which emerged in late spring, is intermediate.

To see where this butterfly has been reported, visit:  The Ontario Butterfly Atlas Online

For more info on this species, visit the Butterflies of Canada