Papilio glaucus: this far north?

In the last week I have seen 2 adult Tiger Swallowtails. This seemed odd to me because, as far as I know Papilio canadensis is a univoltine species (at least up here around Ottawa) and it's flight period should have ended by now. See my earlier post on swallowtail cohorts.

Aside: voltinism is the number of generations a species of butterfly (or other taxa) has in a year. Univoltine species have one generation in a year, bivoltine have 2, mutivoltime have >2, and semivoltine have <1. 

I recently learned from the folks over at eButterfly that for the last 4-5 years or so Papilio glaucus has occurred around the Ottawa area, overlapping in distribution with Papilio canadensis. Apparently, Papilio glaucus is bivoltine (even this far north), so the adults that I have been seeing are Papilio glaucus adults from the second flight period. It is worthwhile noting that I have also seen many Papilio polyxenes fluttering around.

Papilio glaucus, adult female. Probably attacked by a bird. Photo taken July 15 2012

Below is my recent Twitter correspondence with the experts at eButterfly:

Thomas Hossie ‏@hossiet13 Jul

Saw a Papilio canadensis adult today? I thought they'd be done by now up here just south of Ottawa. @eButterfly_ca @bug_girl@weirdbuglady

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eButterfly ‏@eButterfly_ca14 Jul

@hossiet Hi Thomas what you saw is the Eastern Tiger Swallowtail ( Papilio glaucus) , there second generation is just starting

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Thomas Hossie ‏@hossiet

@eButterfly_ca P. glaucus is bivoltine this far north (i.e. Ottawa)? Also, I thought that P. glaucus was replaced by P.  canadensis up here

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eButterfly ‏@eButterfly_ca14 Jul

@hossiet we have now had P. glaucus in Ottawa for 4-5 years with each year they are becoming more common.

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eButterfly ‏@eButterfly_ca
14 Jul

@hossiet P. glaucus overall habitus is bigger, the row of yellow spots on the outrr edge of the upper wing are linked and...

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eButterfly ‏@eButterfly_ca14 Jul

@hossiet only P glaucus has a second generation so with few exceptions, any fresh tiger swallowtail in july is P glaucus

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eButterfly ‏@eButterfly_ca14 Jul

@hossiet yep they do hybridize which makes it very hard to distinguish them in the spring when both are on the wing.

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