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HOW TO REAR SATURNIID MOTHS (giant silk moths)

Beginner-level info for rearing Polyphemus, Luna, Cynthia, Cecropia, Promethea, Io, Regal, and Imperial moths. (The first 3 species are the easiest to rear.)

by Liz Day (Copyright 1998-2007; ask for permission to reproduce.) Last updated April 5, 2007.

Full grown regal moth caterpillar (about 5" long). Photo by Ron Foster.

Large (4th instar) cecropia moth caterpillar. First and second instars of cecropia. Note how different the young larvae look from the later stage. Photos by Betty Cessna.

Female imperial moth laying eggs on a wall in Florida (not normal behavior, but a good closeup). Photo by Abhijit Wakchaure.

GREAT NEWS!!! "Field Guide to Moths of Eastern North America" by Covell is now back in print! I recommend it. Available on Amazon.com. For more detail on saturniid moths, get "Wild Silk Moths of North America" (1996) by Tuskes, Tuttle, and Collins. For caterpillars (both moths and butterflies), get "Caterpillars of Eastern North America" (2005) by David Wagner.

There are very few good guides to moths or larvae; these are among the best.

A link to a mailing list about raising silkmoths: click here

COMING SOON...:-)

TABLE OF CONTENTS

Store cocoons outdoors, in the shade, in a rodent-proof cage. Use a
container that "breathes" well, not one that is airtight.
Cocoons can also be put in an unheated garage or porch, if the container
is such that animals can't get them. (In a garage or porch, choose
a shaded place, because even in winter, sunlight is hot.)
Birds, coons, mice and chipmunks eat pupae! One can make a cage
out of hardware cloth (coarse screening found at hardware stores).
Such a cage is also useful for containing the moth when it hatches.
Do NOT put cocoons in a frost-free refrigerator (except in containers
as described below); they'll dehydrate and die. The cocoon helps
protect the pupa from drying out (this is why above-ground pupae have
cocoons, while below-ground pupae are naked), but it still allows some
water vapor to leave, so it cannot protect them completely from the
perpetual dryness found in a frij.
Luna moths make thin cocoons which are normally covered in leaf litter
in the wild. Put some oak leaves, which don't get wet easily, around
them to protect them from the weather.
Give imperials & regals about 6" of moist peat moss to burrow
into, where they will pupate. Peat moss, which is fairly germ-
free, seems better to me than soil, which is not very clean.
Avoid vermiculite and other materials that are too loose/coarse
to hold their shape. If the little cave that the larvae has dug
collapses on it, the animal can get deformed when it molts into a
pupa.
Even if there is nowhere to dig into, the larva will eventually
pupate anyway. Thus, you can also just put the larvae in a
container with damp paper towels and let them pupate in "the
open". Make sure there is humidity. This is a good way to observe
the molting, which is strange to see.
After they dig in, you should wait at least two weeks before
disturbing them, since they may still be soft under the ground.
The caterpillar molts into an egg-shaped pupa that first is
greenish, then turns dark brown and hardens.
Their winter care is something of a pain. My friend had nearly
all of his rot over winter for several years until he discovered
how to keep them.
He stores imperial and regal pupae in the frij, in a special
Tupperware arrangement. (If pupae sit in the open in a frost-
free frij they will dehydrate and die.) Get a piece of 100% linen
(avail at bridal stores). Linen will not get wet in damp air.
Put a small amount of water in the bottom of the Tupperware
container. Put the pupae on the piece of linen, lay the linen
over the open top of the plastic container like a hammock, and
close the lid, trapping the edge of the linen in the lid to
keep it from falling down. The pupae are now suspended in mid-air
inside the container.
illustration
The linen does not get wet, but
the air is kept humid. I open the container every two weeks,
check the water level, and blot up any condensation on the lid
or the pupae. This system should also work for other species with
naked pupae.
My friend does not put air holes in the container. However, I
fear that they could eventually suffocate if sealed up for too
long. So I open the container every so often. Or you could put in
some air holes.
Regal and imperial pupae can take freezing temperatures in the
frij, but not for very long. Keep the temp above freezing.
When it gets cold outdoors, that is the time to start the pupae's
cold period. They need to be acclimated to cold. Keep them
somewhere where they will gradually get cold over a period of at
least a week, as it does outdoors, before putting them in the
frij. In spring, take them out of the frij when it warms up
outside. Put the pupae back into peat moss, in a flowerpot,
inside a cage, outdoors. Water it often enough to keep them
from drying out. The adult is able to crawl out of the peat when
it hatches. Supposedly the pupa works its way to the surface,
using its tail spine, just before the moth emerges.
Remember that since regal and imperial moths have only one brood a year,
and the moths fly in mid-summer, your pupae will sit there in the potting
mix until July or August.
For more info on winter storage of pupae, see Bill Oehlke's site:
click here
He supplies similar conditions in a slightly different way.
A good description of how regal moths pupate, with photos, plus more
rearing info, are on Adam Fleishman's site, which moved and I have to find
where it went, link will return when I do.
To see if a pupa is alive or dead, carefully poke it in the
leathery area between two abdominal segments with something dull
like your fingernail or the edge of a piece of paper. They hate
this; live ones will squirm. Other clues: live ones weigh more
(they sink in water) and are glossier than dead ones.
All the native large saturniids overwinter as pupae, never as
eggs.
Things to see:
Watching the larva actually shed its skin and become a pupa is a
strange experience. The new pupa is not smoothly fused together
over its surface - the head, antennae, and wings are still
detached at first and the very soft pupa slowly pulses and
scrunches its head into a concave position like a rubber toy
being punched in. To see this, however, you must cut open the
cocoon (maybe they could be induced to spin one against something
transparent?), dig up the prepupa from the soil, or have allowed
one to pupate in an empty container as described earlier for
regal/imperial moths. There is danger of injuring the animal;
also, before you disturb it, be sure the pupating larva has
become a prepupa and is no longer able to walk. Otherwise,
finding its cocoon gone, it will spin another one, using up a lot
of its energy reserves.
One spiracle is in front of the wings.
To sex pupae, look at the underside near the tail. 4 abdominal
segments below the wingcase, there is an area where the edges
separating the segments seem to disappear or run together down
the center. In females, this area is smooth and blank. In males,
there are two little bumps right next to each other, where the
genitalia will be. Also, the males' antennae are much wider than
the females'.
I am told that in luna moths, the larvae that are going to diapause
turn brown just before they pupate, wander off the food plant, and
spin darker-colored silk. Those that plan to hatch without hibernating
stay green, make a cocoon right in the leaves, and spin lighter-colored silk.
However, I am not sure this is completely reliable, as I have had cocoons
do the opposite of what was expected.
Some species spin a silk attachment tying their cocoon to the
main twig, so when leaves drop in autumn it will stay up in the
tree.

One can indeed get silk from the cocoons of these "giant silk
moths". However, the silk is a different grade from that made by
the (unrelated) domestic silk moth raised in China.