biologia i zachowanie jedwabników

Biology and behaviourof the silkworms

Małgorzata ŁochyńskaSilkworms Breeding and Mulberry Cultivation LaboratoryInstitute of Natural Fibres and Medicinal PlantsWojska Polskiego 71B60-630 PoznańPOLAND

The egg of mulberry silkworm is oval, 1,5 mm in diameterand has a distinct hollow in the centre.There are about 1 500 eggs in 1 gram.

Inseminated eggs.

Uninseminated or just laid eggs.

Mulberry silkworm (Bombyx mori L.)

Department of Silkworms Breeding and Mulberry Cultivation INF&MP

In spring the caterpillars hatch from the eggs. They are 3 mm long. They start eating at once.

After 28-34 days the caterpillars become mature, 8-10 cm long.

During the caterpillars’ live, there are 4 moults after 4-7 days.

During the moult, the caterpillars stick to leaves with silk fibres

and rise their heads, where they have a

characteristic triangle of snapped epidermis.

The caterpillar comes out from the old epidermis, called indusium, which was sticked to leaves.

The caterpillar’s epidermis has a very various pigmentation: white, black, speckled or without pigments. It is a feature of variety.

After 28-32 days the caterpillars lose

their appetite,they become

yellow and the epidermises are

transparent. That means, that they are ready to

spin their flosses.

Just before spinning, we put the wood ladders, on which the caterpillars spin their flosses.

A cocoon is a floss with a caterpillar, chrysalis or butterfly inside and the epidermis after the last moult.

Two salivaries, spinnerets, produce

the silk fibre. They are 5 times longer than the

caterpillar’s body.

Two single silk fibres (from two salivaries) are sticked in one double fibre.

The silk fibre is made from the white, unsoluble in water fibroine. Liquid fibroine get harden under

the activity of oxygen. This proteine is covered with a yellow-coloured sericine (proteine glue).

During spinning the floss, the caterpillar

sticks the silk fibre on the edge of the wood ladder.

First it makes a dense net, called a floss,

and then hangs the cocoon on it.

One caterpillar can produce the silk fibre, which is 500-3 500 m long.

The caterpillar transforms into the chrysalis inside the cocoon and it undergoes a complete metamorphosis. After 2-3 weeks, the chrysalis transforms into a white butterfly.

The butterfly melts the top of the cocoon and goes out. It lives 10-30 days. The female has bubble aromatic salivaries, which produce an aroma, that attracts a male.The wing span of this moth reaches 4 cm but it has no ability to fly.

The butterflies make a pair at once and start copulation.

After copulation, a female lays about 500 eggs in 2-4 days.

One female can lay 400-600 eggs.

After winter, a new generation of caterpillars hatchesfrom these eggs.

The egg of the oak silkmoth is 5 mmin diameter.

There is about 120 eggs in 1 gram.

Oak silkmoth (Anthereae pernyi G.)

After 8-14 days, the black and dense haired caterpillars hatch from the eggs.

After 5-6 days, the caterpillars undergo

the first moult and become yellow.

There are 4 moults during the caterpillar’s live.

The moult lasts 2 days. At this time, the caterpillars

„freeze”and do not eat.

The caterpillars just before and after the second moult.

The caterpillars before and after the third moult.

The caterpillars are covered with sparse and thorny hairs.

Frightened caterpillars freezeand their hair stands on end.

The caterpillars eat the leaves and small

branches of oak and birch.

After 35-60 days from the hatch, the caterpillars grow to 15 cm.

They become mature and spin the flosses.

The cocoons are sticked to the branches.

The cocoons of oak silkmoth are very irregular. They have

holes, loops and weaved leaves and branches.

The cocoons are white- or beige-coloured.

The cocoons of oak silkmoth contain less silk fibre than the cocoons of mulberry silkworm.

However oak fibre is stronger and more resistant to acid and alkali activity.

Oak fibre is 3-4 times thicker than mulberry fibre.

Oak silkmoth spends winter as the chrysalisin the cocoon.

Even when the teperature drops to –20o C, the chrysalises are safe.

Transformation of oak silkmoth’s caterpillar into the chrysalislasts 7-9 days.

After 2-3 weeks, the butterflies melt the cocoons and go out.

The wing span of a butterfly reaches 15 cm. Unlike mulberry silkworm, this moth has the ability to fly.

The butterflies make a pair and start copulation.

After 24-36 hours,a female lays eggs.

The oak silkmoth species gives two generation per year.

After 8-10 days, an autumn

generation of black caterpillars hatches

from the eggs.

Mulberry silkworm (Bombyx mori L.) and oak silkmoth (Anthereae pernyi G.)

The chrysalis and cocoon ofmulberry silkworm and oak silkmoth

The cocoons, from the mulberry silkworms breeding at INF&MP,

will be used in:The cosmetics industryThe textile industryThe production of wear (scarves, ties)The production of surgical threads.

biologia i zachowanie jedwabników

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