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Silk

A photograph of a male silkworm moth (_Bombyx mori_) and two cocoons

A male silkworm moth (Bombyx mori) and two cocoons

Introduction

Silkmoths - the term describing moths whose pupae are surrounded in a silken cocoon - are represented by members of the Bombycidae and the Saturniidae. Both Families are farmed for their silk; the silk of the former being more highly regarded - both for the quality and quantity of silk produced. The Silkworm moth (Bombyx mori Latr.) being the most frequently exploited member of the Bombycidae. The Saturniid moths, especially within the genera Samia and Antheraea, produce Tussore silk.

There are about 1300 species within the Family Saturniidae, although only a small percentage of these produce silk. The majority of them are sub-tropical and tropical regions. The silk moths surround their pupae with a silken cocoon; the remainder of the Saturniidae have larvae which pupate underground and don't produce cocoons. When the cocoons are boiled the silk can be unwound and collected for treatment.

Characters of silkmoths

Large moths, without a frenulum (a row of bristles) linking the wings. The two pairs of wings are synchronised by an overlap of the anterior (front) margin of the back wings, helping to hold them against the front wings. The wings are attractively patterned and frequently possess an 'eyespot'. Males (and sometimes females) have feathery antennae.

Larvae are large, measuring up to 10cm when fully grown. They are voracious eaters of leaves of their food plant and many eat a number of different plants. In captivity they will eat Holm oak and mulberry.

A photograph of an Actias maenas larvae

Economic importance

Silk has a long tradition of commercial production, dating back some 2500 years and silk is known to have been used for 2000 years before that. It originated in China where its universal appeal led to the development of the 'Silk Road' - from Xi'an to Rome and then across the Atlantic.

The silk trade is now a multi-billion dollar industry and silk is produced commercially by Japan, India, South Korea, the Commonwealth of Independent States and Brazil, as well as in China.

The commercial production of silk is called Sericulture.

Breeding silkmoths

Larvae commonly accept a wide range of food plants in captivity, especially holm oak and mulberry, but may not be happy if forced to switch from one to another. Prior to pupation, they stop eating for a few days and then attach themselves to some of the twigs of the food plant whilst spinning a silk cocoon around themselves.

Some species spend two winters in the chrysalis, and some (e.g. the North Chinese silkmoth, Antheraea hartii) require a dramatic increase in temperature in order to trigger emergence. Place the pupae in a cold, frost-free environment, eg. a shed and, after a week or so, bring them into a temperature of about 26°C.

We also have an online caresheet for Moon Moths, a type of silkmoth.

Essential reading from the Amateur Entomologists' Society

Related links: Silk

Bibliography

Rearing wild silkmoths
Baxter, Ronald
Chudleigh Publishing, 1992

Saturniidae Mundi: Saturniid moths of the world 3 vols.
d'Abrera, Bernard
Hill House Publishers, Vol. 1 - 1995-

The story of silk
Feltwell, John
Alan Sutton Publishing, 1990

Sericulture training manual
Food and Agriculture Organisation

A Silkmoth rearer's handbook
Gardiner, B.O.C.
AES, 1982

A practical guide for raising and utilizing silkmoths and honey bees in Africa
Raina, S.K. and Jones, Richard
WHSmith

Sericulture and silk production: A handbook
Shekar, Prabha and Hardingham, Martin
WHSmith

Sericulture: The proper employment of women in 19th century China
Wright, Grace
WHSmith