(Continued from Part Two)
Think back to late May and early June of last year. This was
the time when one would have observed the first monarch
butterflies reaching northeastern Wisconsin for the summer
months. Chances are extremely slim that any of them had flown
all the way from, for example, the Sierra Chincua Sanctuary, the
largest and most pristine monarch overwintering area in
north-central Mexico.
There are records of tagged monarchs--having been tagged the
previous late summer or early fall in northern U.S. and spending
the winter in Mexico--of reaching a point around 1000 miles north
of their wintering site the following spring. The general
accepted thought is that the monarchs have no natural instinct to
mate and to lay eggs all during the winter months spent at
approximately 10,000 feet elevation at an average temperature of
around 50 degrees F.
Finally, around March 21, the Spring Equinox, the butterflies
begin flying northward and mating. In fact the females are
literally forced to continue flying until they come to the first
milkweed plants upon which they will lay their eggs and then die.
Upon hatching, the total time required for the caterpillars to
shed their skin five times (each shedding referred to as an
instar), enter into the chrysalis or pupal stage, and finally
emerge as an adult monarch will require around four weeks. They
now will head northward and be the butterflies that will arrive
in Wisconsin usually in late May to early June. They will
immediately mate and start another new generation.
There are still many mysteries surrounding the monarch
butterfly, one being its ability to fly 2000+ miles southward in
fall to the monarch wintering sites in Mexico, never having been
there before, and then reversing their direction of migration by
180 degrees the following spring and heading northward. One
widely accepted thought is that the knowledge of where to go is
imbedded in crystals of magnetic minerals in their bodies.
The Spencers have a great plenty of common milkweed plants
(the least favorite) on which monarch eggs have been laid and
where the caterpillars will eat their fill of leaves. Also
available are swamp milkweeds (the second most favorite) as well
as the Mexican milkweeds, the latter being the top favorite of
the monarch females upon which they will lay their eggs.
A large cage made with a sturdy wooden frame and aluminum
screening, is approximately two feet wide, two feet high and four
feet long. A two-foot-wide side section is made to be a hinged
door. The bottom consists of a sturdy piece of fiberglass that
can be slid out for regular cleaning. Slots are cut into the
bottom end-piece of the frame and into both bottom side-pieces of
frame in which the fiberglass bottom can easily slide without
having to open the door.
Several narrow strips of wood run across the from the top of
one bottom side-piece to the other on which quart fruit jars for
holding the swamp milkweed plants (in water) can be placed. By
suspending the jars off the bottom, the bottom can then be slid
out for cleaning. A lot of droppings, called frass, will be
given off by the voraciously hungry caterpillars and this must be
cleaned out of the cage regularly in order to prevent diseases
from spreading into the caterpillars or emerged butterflies.
Generally the caterpillars are left to almost eat their fill
on the milkweed plants growing in the Spencer’s large butterfly
garden. When it appears that the caterpillars are just about
ready to shed their skins for the fifth and last time, they are
collected and placed inside the rearing cage. The swamp
milkweeds are the preferred plants to have inside the cage where
they are placed in water-filled quart fruit jars whose tops have
been securely closed around the stems of the milkweeds and
tightened around the tops of the jars with rubber bands. Do not
allow the milkweed plants to touch the top of the cage.
The cage must be built very tightly in order to prevent the
caterpillars from escaping. Provide them with ways of climbing
down the sides of the jars and up to the top of the cage where
they will attach them selves onto the screen, form into their
characteristic "J" shape for around eight hours, and
then in around two and a half minutes shed their skin for the
last time, form into their famous jade-green, gold-studded
chrysalis and quite miraculously develop into an adult monarch
butterfly in around ten or more days.
Allow the butterflies to harden their wings for several hours
or overnight, provide some good nectar-rich flowers for them to
feed on, and, with the weather sunny and fair, release them to
their freedom. It is guaranteed that rearing monarch
caterpillars will become one of the most exhilarating and
environmentally helpful hobbies you have ever undertaken.
Monarch chrysalids in various stages of development
dangle safely from the top of the rearing cage.
Our friends, the David Spencer family from near Fremont,
Wisconsin have learned a great deal over the past several years
about rearing monarch caterpillars. They do it very
scrupulously, primarily to insure a higher rate of success in the
complete metamorphosis of the butterfly: from egg to caterpillar
to chrysalis and, finally, to adult butterfly. Depending upon
which species of milkweed the caterpillar is eating in the wild,
it can be completely free of cardiac glycosides and be perfectly
suitable for a bird to eat, or it can be loaded with the
glycosides and cause the eater to go into virtual fits of
vomiting. Once a bird bites into one of the glycoside-laden
monarch caterpillars or adult butterflies, you can be assured
that it will be the last one it will touch.
This column appeared in the Door County Advocate
on 04/05/2002.
© Copyright 2002 Roy Lukes. All rights reserved.
