Zebra Swallowtail (Eurytides marcellus) 

Member of Family: Papilionidae 

The first generation of the season has shorter tails, as shown at upper right.  Later generations have longer tails, as shown in the other images ( from further south ).  This species is probably not resident in Canada, but occasionally strays into extreme Southern Ontario from the US, where it is fairly common.  I have not yet seen this species in Canada.

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