The interval
between moults is called an instar. An instar is a stage within a stage. At
the end of each instar, the silkworm sheds its skin, enabling growth to
continue. During the shedding of the
skin the silkworm appears "asleep".
It stops eating. It is torpid (appearing "frozen" in space) resting on the branch, often with its head slightly raised. It's best not
to disturb the silkworm during this time.
After the moult it will happily start munching the mulberry leaves again.
The following is an approximate record of the instars of my silkworms.
First Instar Day 1 to
approx. day 4
After
hatching from the egg until the first moult, is the 1st Instar.
The color of
the silkworm is blackish and the head is black.
Second
Instar Approx. day 5 to day 11
The period
between the first and second moults.
Third Instar
Approx. day 13 to day 18
The period
between the second and third moults.
The color of
the silkworm is grayish-white. The black head has changed to brown (after leaving the little black "cap" behind.
The stripes of the zebra silkworms are showing.
Zebra and the plain silkworms.
Fourth
Instar Approx. day 20 to day 26
The period
between the third and the fourth moults.
They liked to use the stalks as highways!
Fifth Instar
Approx. day 27 to day 35
The period
between the fourth moult and spinning the cocoon.
My silkworms just kept eating and eating! I understand the silkworm does 80% of its eating during this
fifth instar and the silk glands now make up 25% of its body weight. My largest silkworms were 7cms long, about
the size of my little finger. They took their time before
starting to spin...seemed too happy munching!
During this lava stage, the silkworm grows from about 3mm at
hatching, to about 7cms in length. It
increases it's original size 10,000x by the time it is ready to start spinning
its cocoon! Most of this growth is during the fifth instar.
Photography: M. Vaughan.
beautiful
ReplyDeleteNice and valuable info.
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