Papilio glaucus diapause?

[Kurt Jacobs]

I would like to take a stab at this and would appreciate it if anyone can
correct me or elaborate further.  Hope someone didnt go into detail below,
as i am behind on the reading, but see nothing connected to the thread.
Dont you just love it when physical sciences people start writing about
biology.  I understand most of this is old hat to many.

The following does not take into account temperature or humidity or host
plant influences, just assumes that the species is reared in its most common
natural conditions.  In other words, im only talking about light here.

Some species of lepidoptera are univoltine. I believe univoltine means they
can diapause, but someone needs to define this word, as its not in my
Websters(also volt signals something with energy, so maybe it has something
to do with light, help). Many species have a facultative day-length
controlled diapause.  This means that the amount of light received by the
larvae has an effect on whether the pupae enters into diapause or not.
Some species have sharp cutoff points on the amount of light received by the
larvae, which means that if you drop below a certain day length, just about
every pupae will enter into diapause. Other species have larvae for which a
greater and greater percentage of the pupae enter into diapause as the day
length is decreased.  If the LARVAE (stressing larvae, but please correct me
if the day light hitting a pupae can do anything but warm it and give it a
tan) are subjected to a long enough period of light during their
development, most if not all of the pupae will emerge within a relatively
short period of time (two weeks to a month) constituting a new brood for the
season.  This of course is common sense since long daylights usually mean
that summer is still in full swing.  As the hours of daylight decrease, a
greater percentage of the pupae enter into a diapause, but many will not and
will still emerge.  That way if their is an exceptionally long and warm
fall, a new brood can develop, while the pupae that entered diapause may dry
out.  As the daylight hours are further reduced, nearly all of the pupae
will go into diapause, but 1% still might not.  When the pupae is in
diapause, some condition must break it, usually a long cold period.  Some
species however are obligatory univoltine, which means they are going to
enter diapause no matter what the light conditions are. Hyalophora cecropia
is a great example of an obligatory univoltine.

It is certainly way more confusing than this.  Every species has its own
diapause graph, a graph of percentage in diapause vs. the hours of light per
day.  To really confuse the whole argument, Bombyx mori enters into diapause
as an egg.  And the more light per day the larvae experience, the more that
go into diapause.  WOW.  So you can see that it is really a species specific
problem.

Which leads me back to the question of Papilio glaucus.  Can someone please
comment on the specific behavior of this species and also Papilio polyxenes
and Papilio glaucus canadensis.  I do not have any good reference on the
rhopalocera (butterflies).  My reference for the above was the Silkmoth
Rearers Handbook(Gardiner, 1982). An inexpensive and great general reading
book on silkmoths.