Achyra affinitalis (Lederer, 1863)
Cotton Web Spinner
(one synonym: Nymphyla sordida Butler, 1886)
Don Herbison-Evans
Stella Crossley

Achyra affinitalis
(Photo: courtesy of Nadine Brown, Swan Reach, South Australia)

These Caterpillars are greenish brown, sprinkled with darkish dots, and with yellow between the segments. The underside is paler than the dorsal surface. The head is brown. The caterpillars are agricultural pests, attacking crops such as :

  • Sunflowers ( Helianthus annuus, ASTERACEAE ),
  • Alfalfa ( Medicago sativa, FABACEAE ),
  • Flax ( Linum usatissimum, LINACEAE ),
  • Cotton ( Gossypium hirsutum, MALVACEAE ), and
  • Sorghum ( Sorghum bicolor, POACEAE ),

    living communally in a silk web built on the plant. In the wild, they have been found feeding on :

  • Saltbush ( Atriplex, CHENOPODIACEAE ).

    The caterpillars grow to a length of about 2 cms.

    Achyra affinitalis
    (Photo: courtesy of Donald Hobern, Australian Capital Territory)

    The adult moth has forewings that can vary from fawn, through rusty brown, to dark brown, sometimes with a pattern. The hindwings are pale brown with a satin sheen. The moth has a wingspan of about 2 cms.

    Achyra affinitalis
    (Photo: courtesy of CSIRO/BIO Photography Group, Centre for Biodiversity Genomics, University of Guelph)

    It is a very common species in eastern Australia, and is probably the most widespread and common Crambid in Australia.

    Achyra affinitalis
    (Photo: copyright of Brett and Marie Smith, Ellura Sanctuary, South Australia)

    The moth appears to be able to fly long distances, as outbreaks of this pest occur in diverse areas. Its coverage includes:

  • New Zealand, and even
  • France,

    Achyra affinitalis
    mating pair
    (Photo: courtesy of John Bromilow, Ainslie, Australian Capital Territory)

    but it appears to have originated in Australia, being found in:

  • Northern Territory,
  • Queensland,
  • New South Wales,
  • Australian Capital Territory,
  • Victoria,
  • Tasmania,
  • South Australia, and
  • Western Australia.

    Achyra affinitalis
    drawing by Julius Lederer, listed as Botys affinitalis
    Wiener Entomologische Monatschrift,
    Band VII, Part 11 (1863), Tafel 12, fig. 4,
    image courtesy of Biodiversity Heritage Library, digitized by Ernst Mayr Library, Harvard University.

    Further reading :

    Ian F.B. Common,
    Moths of Australia, Melbourne University Press, 1990, Fig. 33.20, pp. 66, 354, 357.

    Julius Lederer,
    Wiener Entomologische Monatschrift,
    Volume 7, Part 11 (1863), pp. 475-476, No. 84, and also Plate 12, fig. 4.

    Peter B. McQuillan, Jan A. Forrest, David Keane, & Roger Grund,
    Caterpillars, moths, and their plants of Southern Australia,
    Butterfly Conservation South Australia Inc., Adelaide (2019), p. 86.

    Australian Butterflies
    Australian Moths

    (updated 4 April 2013, 19 March 2017, 2 September 2019, 3 July 2020)