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 canadensisApparently, 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:

Saw a Papilio canadensis adult today? I thought they'd be done by now up here just south of Ottawa.  
 Hi Thomas what you saw is the Eastern Tiger Swallowtail ( Papilio glaucus) , there second generation is just starting
 P. glaucus is bivoltine this far north (i.e. Ottawa)? Also, I thought that P. glaucus was replaced by P.  canadensis up here
 we have now had P. glaucus in Ottawa for 4-5 years with each year they are becoming more common.
 P. glaucus overall habitus is bigger, the row of yellow spots on the outrr edge of the upper wing are linked and...
 only P glaucus has a second generation so with few exceptions, any fresh tiger swallowtail in july is P glaucus
 yep they do hybridize which makes it very hard to distinguish them in the spring when both are on the wing.


Post a Comment