Mythimna convecta (Walker, 1857)
Australian Armyworm
(one synonym : Pseudaletia evansi Holloway, 1977)
Don Herbison-Evans
Stella Crossley

Mythimna convecta
(Photo: courtesy of the Macleay Museum, University of Sydney)

This Caterpillar is brown, with dashed black stripes along the back, and two wide pale stripes along the sides. The two dorsal stripes continue over the thorax and head. The head is also stippled in black and brown.

Mythimna convecta
close-up of head and thorax
(Photo: courtesy of David Akers, Won Wron, Victoria)

It is an agricultural pest, causing damage to pastures and crops. It hides by day, and feeds nocturnally on many plants, including :

  • Pineapple ( Ananas comosus, BROMELIACEAE ),
  • Sweet Potato ( Ipomoea batatas, CONVOLVULACEAE ),
  • Alfalfa ( Medicago sativa, FABACEAE ), and
  • various Grasses and Cereals ( POACEAE ).

    They are called 'Army Worms' because of their habit of spreading out in a line across a lawn or pasture, and marching across it (somewhat slowly) consuming the foliage as they go.

    Mythimna convecta
    (Photo: courtesy of the Macleay Museum, University of Sydney)

    The pupa is brown, and formed in a light cocoon in a cavity excavated just under the soil surface.

    Mythimna convecta

    The adult moth has slender speckled rusty brown forewings with variable vague markings, each forewing usually with a black-edged white dot near the middle, next to a reddish smudge. Sometimes it has an angled submarginal line of dark dots. The hindwings are buff with dark veins and a broad dark margin. The hindwings have sinuous margins. The moth has a wingspan of about 4 cms.

    The species is migratory, and occurs across most of Australia, including

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

    Mythimna convecta
    (Photo: courtesy of the Photography Group, Centre for Biodiversity Genomics, University of Guelph)

    Attempts to control the pest include :

  • using a garden roller at midnight (when they are attacking a lawn),
  • digging post holes for the larvae to congregate in during the daytime, where they may be crushed,
  • laying some sacking near the plants attacked, so that the Caterpillars will hide under that by daytime, and they may be then collected and disposed of,
  • various chemical insecticides
        (chlorpyrifos, alpha-cypermethrin, trichlorfon, carbaryl, methomyl)
  • a nuclear polyhedrosis virus,
  • the fungus Nomuraea rileyi,
  • the nematode Steinernema carpocapsae ( STEINERNEMATIDAE ),
  • a wasp Netelia species, ( ICHNEUMONIDAE ),
  • the wasp Apanteles ruficrus ( BRACONIDAE ), and
  • various flies, including Ceromya horma ( TACHINIDAE ).

    Mythimna convecta
    (Photo: courtesy of Joan Fearn, Moruya, New South Wales)

    Further reading :

    Ian F.B. Common,
    Moths of Australia,
    Melbourne University Press, 1990, fig. 50.2, pp. 45, 56, 59, 65, 466.

    Peter Marriott & Marilyn Hewish,
    Moths of Victoria - Part 9,
    Cutworms and Allies - NOCTUOIDEA (C)
    Entomological Society of Victoria, 2020, pp. 25, 28-29.

    Francis Walker,
    Catalogue of Lepidoptera Heterocera,
    List of the Specimens of Lepidopterous Insects in the Collection of the British Museum,
    Part 11 (1857), p. 711.

    Australian Butterflies
    Australian Moths

    (updated 12 January 2013, 4 September 2023)