Polyphemus / voltinism

[Martha V. Lutz & Charles T. Lutz]

Chris wrote:

"I've raised 30 polyphemus larvae this season on maple leaves from a female I
obtained and hatched from last season. ( I don't know the food plant she was
reared on)

It's mid August, the larvae just spun cocoons.

I've read and heard repeatedly that in the Boston area that Polyphemus have
multiple broods.  I can't imagine that if my brood should hatch within the next
two weeks into adults and mate that there would be enough time for thier
progeny to mature in time for winter.

They have been raised on fresh cut leaves provided daily and chose maple over
oak, alder, elm and birch. (all of which I provided in an effort to figure out
their prefered food plant)

Q- What should I expect?  How should  I handle these cocoons? (refridgerate?)
If they hatch and mate? will there be enough time before autumn to raise
another brood?  Does anyone know?"


I'll try to respond to the various points one at a time.

1)  Regarding larval food plant of the mother moth:  originally known as
the Hopkins Host Plant Selection Principle (from work done on beetles early
in the 1900s), the concept that what the female fed on as a larva
influences her offspring's food preferences does not seem to hold true for
Saturniids.  That was the focus of some of my Saturniid work with H.
cecropia a few years ago, and larval preference seemed completely
unaffected by what the mother fed on; the biggest effect I found was
hydration level of the leaves offered to the larvae.

2)  It is possible that polyphemus moths have two summer broods in the
Boston area, although it might depend on when the first brood hatches in
the spring.  When did your female hatch?  I have some rearing notes on
polyphemus, and could check them if you would like to know typical
(non-manipulated) durations for larval life, non-diapause pupal phase, and
time required for eggs to hatch.  A female hatching in early May might
produce offspring that would pupate in time for their offspring to be a
second summer brood.  A female hatching in late June . . . probably not,
although some of her offspring might emerge after a month instead of going
into diapause.  Full sibs of Actias luna raised under the same conditions
(in terms of food plant, daylength, and temperature) included both
individuals that emerged after 3-4 weeks as pupae, and other individuals
that overwintered and emerged the following spring (my own work from the
past few years).

3)  My polyphemus like maple (mostly Acer platanoides), but will also feed
nicely on oak (several species).  They will eat black cherry (Prunus
serotina) but if some maple or oak is in the same cage, they will consume
all of that before feeding much on the cherry.

4)  If your larvae just pupated in mid August, then you can expect anything
from all of them emerging to all of them entering diapause.  It depends on
the daylength cues they received.  If they were reared outdoors, I would
guess that some would diapause and others would emerge in mid to early
September.  If they were reared indoors, and you tend to provide a long
'daylength' with indoor lighting, then they may well all emerge in a month
or so.

5)  Rather than putting them in the refrigerator, try putting the cocoons
in a VERMIN-PROOF (very important!!!) cage outside, in a place where they
cannot be flooded by rain but will experience outdoor temperatures.  An
unheated garage works pretty well as a place to put the cage to keep it out
of the rain.  Make sure the cage has provisions for emergence:  something
on the bottom to absorb the fluid they expel when they emerge, and
something for the adults to climb onto and hang from while their wings
expand.  After 5 weeks, maybe 6 to be really safe, you can probably assume
that any that have not emerged have entered diapause.  At that point you
can either refrigerate them OR leave them as is and they will emerge pretty
much in synchrony with the wild population in your area.

6)  I have never, ever had full sibs of polyphemus moths mate.  If anyone
has had them do so, I would greatly appreciate hearing about it!  Lunas
will mate with sibs, and so will cecropias, but not polyphemus.  Which is
interesting, when you think about it!

7)  "will there be enough time before autumn to raise
another brood?  Does anyone know?""


So glad you asked!  In the fall of 1996 someone sent me polyphemus eggs.  I
reared them (indoors, with artificially long days) between mid September
and mid November, and the moths emerged in early December.  Being full
sibs, these moths did not mate.  Regarding the larvae, however:  the larvae
fed happily on maple, continuing to feed even as the leaves turned color
and began to fall.  They preferred leaves fresh from the trees, rather than
leaves that had fallen.  I was able to continue to find hydrated leaves
well into the fall, but also made some 'seal-a-meal-for-bugs' packages.  I
froze fresh leaves and offered the thawed leaves to larvae.  They preferred
individual servings, and would only feed on leaves that were still moist.
Frozen leaves dry out rapidly, so this is a labor-intensive way to feed
(thawing new servings more than once per day as the larvae get big), but
some of these larvae did spin cocoons and emerge as adults--normal, albeit
a bit smaller than their sibs raised on fresh (not frozen) leaves.  The
larvae fed on frozen leaves had a slightly slower growth rate; the larvae
fed on senescing autumn leaves grew at a rate typical of summer brood
polyphemus larvae.


Let me know if you want any more information about this . . . I have about
12 years of data on playing around with Saturniids, their host plants, and
various manipulations with the larvae.  I have even had various Saturniids
feed on Ginkgo and fern, although none ever made it through on those
plants.


In Stride,
Martha Rosett Lutz