Thoas Swallowtail in Oklahoma?

Stelenes at Stelenes at
Sun Jul 18 21:36:36 EDT 1999

You ask if it is possible that thoas make it to OK.  "Possible" would be 1
thoas in more than 10,000 cresphontes, guestimating to make a point only,
based on the language used in the literature.
According to the USGS website mentioned thoas as a very rare stray into OK
and was confirmed ID'ed in two counties (Pittsburg Co. & Cleveland Co.),
probably in or nearly in unique instances.
If you can't get close enough - I suppose the chance is small you might see
the female ovipositing as suggested - or even catch one and examine it - to
see the end of the abdomen of the male which has a distinct chiseled looking
mark on top of cresphontes right near the tip (if something is noted on
observation you can be sure this is it), go by the bands on the upper
Forewing if you have binocs or good, fast eyes.
The dashes forming the band that goes along the cell in thoas looks so nicely
squared and collinear after seeing cresphontes.  In cresphontes those dashes
sometimes are not as collinear and typically instead of squared corners have
diamond shapes especially on the edge of the band opposite of the FW cell.
Also, if you see three prominent dashes forming the submarginal band plus at
most a tiny wanna be fourth one (Perhaps it is best described more like
submarginal dots than a band), it is most likely cresphontes.  However, when
the dots are smaller and not so prominent, this can be more confusing than
helpful.  In the dark versions of both bugs, where the tail is sometimes not
even yellow, it is even harder.
Unfortunately due to the variation, I suspect even an expert would have to
catch and examine carefully the female to ID it as thoas at 100%.  The
observations above can get you confidently to 95% but considering 5% would
still be difficult, I guess that wouldn't prove much.  If the ratio of
species were more respectable, say at least 10/90 you would know pretty fast
that thoas were around!
Take a look at Scott "Butterflies of North America" (1986) and Pyle's
"Audubon Field Guide to North American Butterflies"  (1981, etc. etc.).  I
don't recommend you look at Devries' Costa Rica book, in favor of the OK/KY
ones, though the genitalia info certainly also applies.  Those plates
illustrate a different subspecies of thoas whose range is C.R. into South
America.  They luckily can easily distinguish male thoas because of a yellow
FW cell dot (not sure but doubt the female has one).
Also, practically speaking probably the best clue you would get is that the
thoas would most probably be really beat up to have made it to your place.
(Though Howe mentions that someone saw a thoas oviposit in Colorado in a VERY
unique instance).  So if something is worn down with part of a wing missing
it would get more interesting.
My personal additions to the above and need to be verified are that the
yellow in the thoas is not as intense on the dorsal side and neither is the
black as sooty black on newer ones, sort of a bit less charcoalish.  Plus the
tails seem generally thinner and the yellow color normally present in the
tails is frequently more elongated than circular.  All this may have
something to do with seeing a higher ratio of fresh cresphontes to thoas, but
a gut feel for the species within 200 miles the US-TX border area says there
is more to it than that.
If anyone has more info to add, that would be great.  For example Pyle hints
that the under hindwing row of blue crescents swaps blue for a rust one in
the middle of the chain.  Could be something to this, if we concentrate on
the crescent rather than the large rust one (at least appearing in some
cresphontes, but perhaps not so prominent or organized in thoas) just above
this band.
Happy butterflying.  Doug Dawn.
Woodland CA
Monterrey, MX

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