Eastern/Canadian Tiger Swallowtails

[bree0026 at maroon.tc.umn.edu]

kirk.zufelt at utoronto.ca wrote:
>
> I am interested in opinions in regards to the validity of these insects as
> seperate species. Having lived in the so called "hybrid zone" for many
> years I am confused why all the specimens I have seen are "hybrids".  On
> examining numerous specimens from Southern Ontario I have seen no clear
> Eastern or Canadian Swallowtails they all appear some where in between.As
> you go north they gradually approach the typical "Canadian". The only
> specimens of typical "Eastern's" I have seen are from the Pt.Pelee region
> which is also the only area in the province that has black females.In
> examining specimens from S.Florida,the Carolinas,Missouri,Kentucky & S.&
> N.Ontario it seems to me that there is a gradual change in morphology that
> may accellerate in the Great Lakes Region. I am a "splitter" at heart but
> I find it difficult to believe these are distinct species.
>
> Kirk Zufelt

I'm am also from the "hybrid zone," of N.E. Wisconsin and observed for
many years the butterfly populations of that area.  I'd have to agree
with the split.  Their are two major differences that I've noticed.  The
first is size.  The southern morphology is distincly larger, even in the
"spring" form.  The southern morphology also has the conspicous dark
females.  The other important differnce seems to be in the timing of
flights.  The northern morph has only one flight at this latitude, with a
possible rare double brood.  The southern morph seems to have a full
double brood every year, with a moderate flight in the spring, and a
strong flight in mid to late summer.  The northern morphology has a
differnt flight pattern, with a huge flight in spring, and then nothing
until the next year.  Additionally, there may also be habitat preference
differences and host plant differences, even near the hybrid zone.

Greg Breed,
University of Minnesota Entomology