Silkworms are actually a caterpillar. They are the larvae of the Silkworm Moth Bombyx mori and only one stage of the moth life-cycle.
A silkworm moth lays about 300 eggs, usually in a circular pattern. At the Silk Road, our moths lay their eggs in individual containers so that we can always identify the mother moth! Silkworm eggs are about one millimetre round and if fertilised by a male moth, turn a dark shade of grey within a few days. Eggs that are not fertilised are yellow and will not hatch.
Silkworm eggs lie dormant over winter, awaiting the flush of new leaf on the mulberry tree in spring. At the Silk Road, we store our eggs in the refrigerator for up to 60 days to simulate a cold season.
We then place them in an incubator to simulate spring and provide the right temperature and humidity for hatching.
Silkworm eggs start to hatch 10-14 days after the temperature reaches 22-25 degrees Celsius. They usually hatch only between dawn and noon each day. They are about 2.5mm long, black and covered in tiny hairs. At this early stage they are known as “silk ants”.
As soon as they hatch they start moving around looking for food. At the Silk Road, we get them onto a fresh young mulberry leaf as soon as possible, using a technique called “brushing”. They begin to eat and grow immediately.
As they eat, they grow rapidly and every few days must shed their skin to allow continued growth and development. This is called a “moult”.
Over the course of the larval stage, the silkworm will moult four times. The period between moults is called an “instar”.
When moulting, the worm stops eating and attaches its rear end to a leaf with a thin strand of silk. It sits up in “prayer position” then walks forward as it attempts to wriggle out of its old skin.
The silkworm will grow to around 5-6cm in 27-35 days depending on the type of silkworm.
About 7 days after the fourth moult, the silkworm begins the metamorphosis into a silk moth. Firstly it will stop eating and purge itself of any food still in the intestinal tract. Its shape will begin to change, becoming shorter and rounder. It will then begin to wrap itself in a cocoon of white, yellow or golden silk produced by its salivary glands. Inside the cocoon, its body shape will continue to change and develop the hard brown shell of the pupa.
Inside the cocoon, the metamorphosis into the silk moth Bombyx mori will continue for 10-12 days. The moth then releases an enzyme to dissolve the silk and create a hole through which it can emerge into the world!
Once emerged, the moth must find a mate very quickly as the moths live only 3-5 days.
Bombyx mori has very short wings and cannot fly, thus we need to actively place male and female moths together in the mating trays. Each female will lay around 300 eggs for future silkworm crops.
The cocoon of an emerged moth cannot be used for silk reeling as the long single filament has been broken.