Bombyx mori (Linnaeus, 1758)
Domestic Silkworm
(previously known as : Phalaena mori)
Don Herbison-Evans
Stella Crossley

early instar, drawing by Harold Maxwell-Lefroy
Indian Insect Life: a Manual of the Insects of the Plains, 1909, Plate XXVIII, Fig. 9,
image courtesy of Biodiversity Heritage Library, digitized by NCSU Libraries.

Early instars are off-white and hairy. As the caterpillar matures, it loses the hairs and becomes smooth. The mature caterpillars are buff coloured, with a horn on the tail and brown marks on the thorax. The caterpillars grow to a length of about 4 cms.

Bombyx mori
mature caterpillar
(Photo: courtesy of the Macleay Museum, University of Sydney)

Silkworms are the Caterpillars of the Silkmoth. They were introduced by European settlers into Australia in the nineteenth century to try and create a Silk industry (sericulture). Attempts are still being made to set up a sericulture industry in Australia. Silkworms are also used for educational purposes. The growing of silkworms and the making of silk is extensively illustrated in the BBC video "War of the Worlds", in the "Alien Empire" series. The caterpillars were originally tamed in China, and are now so domesticated that they cannot even hang onto the leaves of their food plant, but have to be kept in cages and have food leaves given to them. The tale of their domestication is part Chinese Folklore.

Bombyx mori
stylised silkworm earings

The caterpillars are often fed on the leaves of plants from MORACEAE, including

  • White Mulberry ( Morus alba ),
  • Black Mulberry ( Morus nigra ),
  • Red Mulberry ( Morus rubra ), and
  • Che ( Cudrania tricuspidata ).

    Young caterpillars will only feed on very young leaves.

    Commercially, the leaves are ground and fortified with flour to make Silkworm Chow. The caterpillars are reported to accept Lettuce, but decline Spinach.

    Bombyx mori
    (Photo: courtesy of the Macleay Museum, University of Sydney)

    The caterpillars pupate in a substantial cocoon, which may be nearly any shade depending on their food and genetics. The thread from a single silkworm cocoon is about 1 Km (10^3 m) long and has a diameter of about 7 microns ( 7 x 10^(-6) m) with a density close to 1.3 x 10^3 Kg/m^3. So a single thread weighs about pi x 3.5^2 x 1.3 x 10^(3 -12 +3) ~= 5 x 10^(-5) Kg. So 1 Kg silk would be produced by approximately 1/(5 x 10^(-5)) = 20,000 silkworms.

    Bombyx mori
    (Specimen: courtesy of The Australian Museum)

    The adult moths are buff coloured, with pale brown lines. Again, the domestication has been so complete that the moths cannot fly. They also have degenerate mouthparts, and so cannot feed. They are totally reliant on the nourishment ingested in their earlier caterpillar stage. The moths have a wingspan of about 4 cms.

    Bombyx mori
    Female, with cocoon and eggs
    (Photo: courtesy of Merlin Crossley)

    The females lay several hundred eggs, which hatch normally in spring. The eggs are white and ellipsoidal, with a length of about 1 mm. The eggs may be kept indefinitely in a refrigerator (not a freezer: that kills them) allowing broods to be obtained at any time of year.

    Bombyx mori

    The caterpillars are attacked by a number of other parasitic insects and diseases, such as:

    The caterpillars are used now all over the world to make silk eg:

  • Brazil,
  • Cambodia,
  • China,
  • India,
  • Japan, and
  • Thailand.

    Bombyx mori
    ( Afghanistan, 1963, courtesy of Poppe Stamps)

    The dead pupae from the unwound cocoons are sometimes :

  • eaten,
  • used in fishing bait,
  • used as ant bait, or
  • used to grow mushrooms.

    Bombyx mori
    Lebanon, 1930

    Further Reading :

    Densey Clyne,
    Angus and Robertson, 1984.

    Ian F.B. Common,
    Moths of Australia,
    Melbourne University Press, 1990, pp. 34, 56, 399.

    Carl Linnaeus,
    Insecta Lepidoptera,
    Systema Naturae,
    Volume 1, Edition 10 (1760), Class 5, Part 3, pp. 499-500, No. 18.

    Peter Marriott,
    Moths of Victoria - Part 1,
    Silk Moths and Allies - BOMBYCOIDEA
    Entomological Society of Victoria, 2008, pp. 24-25.

    Paul Zborowsky and Ted Edwards
    A Guide To Australian Moths,
    CSIRO Publishing, Melbourne 2007, pp. 27, 159.

    Australian Butterflies
    Australian Moths

    (updated 2 May 2013, 4 June 2023)