Mythimna convecta (Walker, 1857)
Common Armyworm
(one synonym : Pseudaletia evansi)
HADENINAE ,   NOCTUIDAE ,   NOCTUOIDEA
 
Don Herbison-Evans
(donherbisonevans@outlook.com)
and
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
(Photo: courtesy of the Macleay Museum, University of Sydney)

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

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

    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 adult moth has forewings that are a speckled rusty brown, each with a white dot in the middle which is outlined in black.

    Mythimna convecta

    The hind wings are buff with dark edges. It has a wingspan of about 4 cms.

    Mythimna convecta
    (Specimen: courtesy of the The Australian Museum)

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

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

    Mythimna convecta
    underside
    (Photo: courtesy of Katherine Chuk, Perth, Western Australia)

    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 ).


    Further reading :

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

    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.


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    (updated 12 January 2013, 1 December 2014)